1.8t Oil Pressure Survival Guide and troubleshooting DIY

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1.8t Oil Pressure Survival Guide
Oil Pressure Warning Light diagnosis and troubleshooting


Table of contents

Introduction
Section 1 - Main Oiling System Components of the 1.8t engine
Section 2 - Understand Oil Flow through the Engine
Section 3 - Basic Physics of Flow and Pressure related to Engine Lubrication
Section 4 - Oil Pressure and Flow within the Engine
Section 5 - General Causes of Low Oil Pressure
Section 6 - The Oil Pressure Warning System and how it works
Section 7 - Oil Pressure Testing and Specifications for the 1.8t (AMB) engine
Section 8 - Diagnosing and Troubleshooting Oil Pressure Problems
Section 9 - Additional Information and Wrap-Up [Time to Wrench!]



Introduction

I remember the first time I got the dreaded “Oil Pressure Warning Light”. I was driving about 15mph in south Baltimore on my way to work going uphill in moderate traffic, enjoying my coffee and then. Beep, Beep, Beep and I see some strange cryptic symbol on the D.I.C. The damn thing scared the crap out of me. A few seconds later it was gone. I pulled over and immediately checked the oil. Full! My car didn't come with an owner’s manual so I was clueless as to what it meant. I tried looking for some info on my phone but after just a few quick reads I had no answers. So I took the back roads to work so I could drive slow and pull over if needed, but made it there without any new problems. So I thought.

It was those initial warnings that eventually lead me to the Audizine Forums. The more I read the more concerned and confused I got. There were dozens of threads about the warning light and oil pressure problems and sludge with the car I just purchased. Being totally unfamiliar with the engine and the community I had a hard time trying to determine how serious a problems I was facing and where to start.

One year later I’ve made a lot of progress and learned many things about how great the B6 and the 1.8T engine is, as well as its weaknesses. I’m still surprised to see new Oil Pressure threads pop up and I wanted to consolidate some of the information here and at other sites to help new 1.8T owners identify and hopefully fix their oil problems before they destroy their fine machine.

My main goal is to simply consolidate as much relevant information possible to help others understand the general concepts of a typical engine lubrication system and help to diagnose oil pressure related problems specific to the 1.8t engine. At a very minimum those seeking help should at least learn the basic relevant components and terminology from this guide and using those terms in the forums while trying to get assistance will likely result in some faster responses from those more experienced members.

While this information is focused on Late Model 1.8t engines and many of the examples and photos used here are specifically for the AMB engine type, I feel that there is a lot of relevant and useful information which would pertain to other engine models.
Before we continue, I will admit that there is very little new information contained within this thread. Everything can be found here on Audizine and the many many other Audi, Volkswagen and car enthusiast websites. I’ll link all of the original sources that I can identify in order to help anyone who is looking for more in-depth research. Also while I am citing and referencing a lot of detailed mechanical engineering information, I am not a mechanical engineer. My background is in Industrial Engineering and Automation and Architecture. I threw away the physics and engineering text books many years ago. If I have included any information which is inaccurate I’ll ask that those more knowledgeable please let me know and I’ll be happy to update this post as often as needed.

ONE MORE THING – if you are reading this guide because you have an oil pressure warning light while driving and you want answers fast, then do yourself a huge favor and stop reading this right now. Find a friend who has one, or purchase an oil pressure test gauge right now. Clicky Clicky You cannot diagnose anything without knowing your oil system pressure. If you went to the doctor for a chest pains and he didn’t have a stethoscope or a sphygmomanometer (The blood pressure tester thing), you would laugh at him! Well if you try to get help here or on any reputable forum, and you do not have this most vital tool then you are not going to get much meaningful help.



Section 1 - Main Oiling System Components of the 1.8t engine

The main engine lubrication components are shown in below (fig 1 and 2) I’m listing only the key components for those totally unfamiliar with the engine.

Oil Pump Assembly #4
Pickup Tube #15
Oil Pump Drive Chain #7
Oil Pump Chain Tensioner #10


Filter Housing #24
Pressure Relief Bypass Valve #4
Oil Cooler #23
Oil Filter #21
Oil Pressure Switch #17


Section 2 – Understand Oil Flow Through the Engine

Most Automotive Internal Combustion Engines follow a fairly basic oil flow circuit. In General oil passes through a pickup tube strainer into the pump then through the oil filter and onto the engine various engine components which require oil for lubrication and or cooling. The 1.8t engine has a fairly familiar oil circuit diagram (fig-3).



From the pump oil flows up the right front side of the block through a Ø12mm gallery and then takes a sharp 90° turn towards the rear of the engine towards the Filter Housing Flange. (fig-4) then into the pre-filtered chamber within the Oil Filter Housing (fig-6 #1)



Within the filter housing oil is channeled to a coupling for the oil cooler where it passes through a small heat exchanger (Oil Cooler) and then into the outside of the oil filter. (fig-7) Oil exits the filter into the center threaded tube and back into the body of the Filter Housing. (fig-8)



After passing back into the filter housing oil enters the Post-Filter chamber (fig-6 #2). This chamber is connected to a spring loaded pressure relief bypass valve. (fig-6 #3) This valve is designed to open when the pump pressure exceeds the flow requirements of the engine. Oil then feeds the main block lower oil gallery to the bearings and splits the flow to the upper oil gallery to the Cylinder Head. Note that there is a small one way check-valve which keeps the oil from draining back from the cylinder head while the engine is off. (fig-6 #4)




From the filter housing oil is passed through a Ø10mm feed line to the main bearings. Oil gallerys are visible along with the return lines which feed from the filter housing. (fig-5)



Also from the filter housing oil is directed back into the block through a Ø5mm gallery into the cylinder head where the camshaft journals, lifters, camshaft adjuster are fed. (fig-9)





Why are there two Pressure Relief Valves? I've tried to find a concrete answer to this question, but to no avail. So I really wanted to know which valve has the lower opening pressure rating.

I was able to test the force required to open the relief valve on my old pump and it appears that the valve opens between 14-20 lbs. My test was very unscientific and involved using a bathroom scale to measure the force, but I think they are accurate enough for discussion. The area of the opening is about 0.77 in^2 so this translates into about 181-259 psi of oil pressure. That amount of pressure seems to be way too high for normal oil bypass. However there seems to be some evidence that the AWM engines according to the Bentley Manual have a bypass valve spec at 12 Bar (174 psi). LINK That's not too far off from my own pump calculation within the margin of error of my simply test.

By searching various parts databases it appears that the oil pump part number 06A115105B (Sec 4 Fig-11) is used in Engine types ALZ AVJ BFB BEX AVB AMB and BKE in model years from 1998 thru 2006. The filter housing part number 06A115405A (fig-6) is used on Engine Types AMB AMU APH ATC AUG AWD AWM AWP AWV AWW BEA and BKF in model years from 1994 thru 2014. Considering that there are no oil fed components between the relief valve within the oil pump and the relief valve within the filter housing, I can only assume that the pump was designed to work on other engines which may not have had a relief valve in the filter housing. It's also possible that valve within the pump is simply a fail-safe for the pump itself, oil filter and oil cooler, where the relief valve in the filter housing is designed to protect the engine components.

I have to assume that the relief valve within the filter assembly would have a lower bypass pressure than the one within the pump assembly. If anyone does have the actual specifications for the bypass valve in the filter housing please post or PM me and I'll cite here. If anyone has an old filter housing lying around and can determine the spring yield force as well as measure the valve piston diameter we can calculate the approximate bypass spec as well.



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Section 3 - Understanding the basic physics of flow and pressure

Oil flow through a system like a car engine is governed by some seriously complicated physics way above my pay grade. Without going into much detail it’s important to at least know some basic concepts in order to have a general understanding of how the system works.

• Fluid Viscosity - Is a direct property of the motor oil type, age, temperature and its level of contamination. General guideline is the lower the viscosity the greater the flow when holding all other parameters the same.
  
  
• Pump Displacement – Mechanical capacity of the pump to move a specific volume of fluid over a period of time or in the case of an engine, per revolution of the crankshaft. Larger Pump and/or Faster Speed equal higher fluid velocity or flow.
  
  
• Fluid Velocity – Simply the speed which a fluid travels. Typical units would be Ft/sec or m/sec. From a practical standpoint pumps MOVE liquid from one place to another. If you had a large piston that you pushed at a speed of 1m/sec without any resistance the water behind the piston would move at the same speed of 1m/sec. Faster speed=faster fluid velocity.
  
  
• Fluid Flow – Volume of fluid which passes through a given area per unit time. On a fundamental level, Flow (Q) = Velocity (V) x Area (A) x Time (t). For example at 6500rpm the oil pump moves oil at a rate 9.61m/sec at the outlet of the pump which is about 12mm diameter (113mm^2) which equals 1085mm^3/sec which can be converted to ml/sec and then 65.2 Liters/min or 17 gpm! (Note: It’s easy to think of flow rate in simple terms like the equation above, however in the real world application like a car engine, flow is resisted by many factors including, shape of the opening, length of piping, surface roughness, turbulence, and viscosity.)
  
  
• Pressure – Simply put pressure is a specific force divided over a specific area. Again you could write your post-doctorate dissertation on the study of oil flow and pressure within the various parts of the engine. To keep things simple, remember that resistance to flow is what creates pressure in the system. Although the relationship is not directly proportional the chart below illustrates the general relationship between Engine Oil Pressure and oil flow/resistance to flow. (fig-10) You should also be familiar with the basic units or pressure measurement. Standard SI units of Newtons per Square meter (Pascals). 100,000 Pascals = 1 Bar which is also approximately 14.5 psi.

Section 4 - Oil Pressure and Flow within the Engine

How the oil pump works to create flow

The AMB engine and most late model 1.8t engines use a Gerator style oil pump. Basically the pump has a 6 tooth gear which rotates eccentrically inside of a 7 tooth internal gear ring. (fig-11) For every 30° of pump shaft rotation a cavity is formed between the two gears and the sidewalls of the pump housing. Because the components of the oil pump are precision machined and clearances between the teeth of the gears are typically less than .075mm a vacuum is created each time a cavity is formed. The volume of this cavity is approximately 2800 mm^3 or 0.0028 liters. As the gears continue to rotate the cavity collapses forcing oil to the pump outlet.



For every revolution of the pump the 7 cavities are formed and collapsed, so the pump displacement per revolution is 0.019 liters. Also note that the pump is driven by a chain sprocket from the crankshaft at 70% of the crankshaft speed. So for every revolution of the crankshaft the theoretical displacement capacity of the pump is therefore 0.014 liters. If you multiply this by 6500 rpm our pump theoretically could move oil at a rate of 89.1 liters/min!

All gearator pumps have a general efficiency rating which is really governed by the amount of leakage (or fluid slip) past the internal pump clearances between the gear teeth and sidewall, which reduce the overall flow. Typically this number for a new pump is 85%. Additionally the density of the fluid being pumped will also change the total amount of fluid displacement. The fluid density of 5w30 at 100dec C is 860 kg/m^3. When you take all of this into account a normal pump should be capable of flowing about 65 liters/min. (fig-12)



It is important to note that Positive Displacement Pumps are “constant flow machines” that is they will produce the same flow at a given speed (RPM) no matter what the discharge pressure. This is the reason that the oil pump has a spring loaded ball relief valve. If the flow requirements of the engine are lower than the flow output of the pump at any given time, the additional flow bypasses the engine and is dumped straight back to the oil pan.


Typical flow requirements for various engine components

If you refer back to the Oil Circuit diagram (fig-3) you’ll realize there there are a lot of engine components which consume oil for lubrication and to dissipate heat. 65 individual components total!

You can see from the chart below (fig-13) that your main bearings and rod bearings consume almost 50% of your oil pump capacity across the RPM range. It should not be surprising, considering that at 6500 RPM the total angular movement of your 5 main bearings and 4 rod bearings is about 456 ft/sec or over 5 miles in one minute! You need a lot of oil flow to lubricate these bearings surfaces.



If you look closely you will notice one important detail from the chart data. In this example at an engine speed around 3000 rpm the oil pressure in the system increases to the point where the required engine flow does not equal the pump flow capacity and at that point the pressure relief valve on the oil pump begins to open. Since the valve is spring loaded the amount of flow which is returned to the oil pan also increases as the rpm’s increase. The flow indicated by the striped red pattern on the upper right is just wasted pump capacity and wasted energy.

Why is the system designed for over capacity? The simple answer is that car makers are aware that over time many factors could influence the flow requirements of the system. So there is some built in over capacity to account for those factors such as bearing wear, pump wear, oil viscosity changes, extreme temperature changes and mechanical failures. Since engine journal bearings by design only work by maintaining a continuous flowing film of oil between the rotating surfaces, the oil flow can never be interrupted during operation.

This is a good time to reinforce the main point. Maintaining proper “OIL FLOW” throughout the lubrication system is the single most important element to achieving proper performance and longevity from your engine.


Oil Pressure within the engine

Now that we understand the flow requirements within the engine we can take a quick look at how the flow within the engine creates pressure within the system. (fig-14) In this graph you can see that oil pressure also increases as engine speed increases. Also like the chart above once the pressure relief valve begins to open above 3000 rpm the pressures begin to level off and are not proportional to engine speed.



Ok so if the above statement is true about pressures leveling off after the relief valve opens, then why does the pressure in the rod bearings continue to increase with engine speed. I have to say I didn’t know the answer to this either when I saw this chart, and it took some time to find the information. Basically the increase in pressure is caused by the centripetal force generated inside of the crankshaft oil gallery to the rod bearing. As crankshaft rotation increases the outward pushing force on the oil towards the rod bearing also increases.



Section 5 - General Causes of Low Oil Pressure

So now we can focus a bit on Oil Pressure. If flow is so important then why worry about pressure? The main reason is that it’s not easy (cost effective) to measure oil flow within the engine. So the common approach is to measure system pressure after the oil filter.

Think about measuring oil pressure to diagnose engine problems as a doctor might measure blood pressure. Since a doctor cannot easily look into your veins and arteries he relies on some very easy to take measurements, usually Pulse and Blood Pressure. High or Low blood pressure is usually not the problem it’s the underlying physiological conditions which are causing the deviation from normal blood pressure which is the real problem. Since a heart is a type of positive displacement pump high blood pressure can be a symptom of some increased resistance to proper blood flow within the body.

Getting back to our engine, high oil pressure is not really a problem in that the design of the system includes a relief bypass valve to bleed off this excess pressure as needed. However, low oil pressure is a symptom of a problem that needs to be addressed.

Hopefully by now the relationship between flow (resistance to flow) and pressure is clear. If we look at each variable individually and isolate all other factors we can discuss all of the factors which reduce flow or increase resistance and subsequently reduce system pressure. I’ve tried to list these in order of the most common and easiest to check.

• Low Oil Level – Pretty simple if the oil level drops below the pickup tube the pump will suck in air and the flow of oil will be reduced. If your engine is equipped with a level sensor and its working correctly you should already know this is a problem.
  
  
• Incorrect Oil Weight – Using an oil with a lower viscosity than the system was designed for, will increase flow, but reduce backpressure. Sounds good so why not simply run lower viscosity oil. You can find some very well written information about this on the BITOG website and I recommend reading the full article when you have time. LINK
  
  
• Oil Viscosity Too Low – In addition to using the wrong or lower viscosity oil as noted above, oil viscosity can change over the life of the oil. Contaminants such as fuel and water, soot, or intentionally adding oil treatments to the sump can lower viscosity. Additionally the longer oil is run its viscosity will be reduced as sheering forces breaking down oil molecules.
  
  
• High Oil Temperature – Pretty basic but to be complete let’s just reiterate that oil viscosity decreases as temperature increases. (fig-15) If you look closely you will see the intersection on the graph for 5w40 motor oil at operating temperature. If your engine is running 15 degrees hotter (which is likely an entirely different problem) you oil viscosity is equivalent to 5w30 motor oil.
  
  
  
  
  
• Incorrect Oil Filter – The 1.8T oil filter has a standard ¾-20UNC threaded boss. There are thousands of filters on the shelf that would fit the housing, but the flow capacity and bypass valve specifications may be significantly different than the correct oil filter. (fig-16) Using a filter with a higher bypass (or no bypass) and or a smaller filter element can reduce flow through the filter. Pressure before the filter would be higher but flow and pressure after the filter would be lower. In the photo below I'm showing a Motorcraft filter next to the Mann W950/4. Do not use the Motorcraft filter. However the Mann W950/4 is an excellent filter. It has the correct bypass rating required for 1.8t and because of it's size it adds about 1/2 qt more oil to the engine capacity, which will increase useful oil life in the engine.
  
  
  
  
  When choosing a filter keep these specifications in mind: The correct oil filter should have a particle filtration rating of 21 micron, bypass pressure rating of 2 to 2.5 bar (29-36 psi), flow capacity of 26 to 35 l/min (7-9 gpm).
  
  
• Malfunctioning Crankcase Ventilation System – The crankcase ventilation system in modern engines is rather complex and the 1.8t engines have a rather convoluted and complex system comprised of over a hundred pipes, hoses, check valves ect. Without going into extensive detail here, the system is designed to direct combustion gasses which are blown by the piston rings and into the crankcase back into the intake system to be burned off. A normally working system will have slight fluctuations between pressure and vacuum which can impact oil pressure by a few psi. As crankcase pressure increases this air pressure pushes down on the oil in the pan increasing pressure into the pump. This is no big deal as a little extra psi of oil pressure isn’t going to hurt anything. When there is slight vacuum pressure in the crankcase this force sucks against the pump suction and may slightly lower oil pressure. The problem can occur if either this positive or vacuum pressure is excessive. Consider that vacuum of 28 in/hg would be equivalent to a reduction in oil pressure of about 14psi which is not insignificant. Here is a great real world example of a forum member troubleshooting this exact problem. LINK
  
  
• Clogged Oil Pickup Screen – Most engine oil pumps have a metal tube with a screen attached to the open end. This screen is designed to keep larger particles about .5mm dia from entering the oil pump. The 1.8t pickup screen is conical in shape and has an area about 1760mm^2. That’s about 15 times larger than the main oil gallery coming from the pump into the block. So the system is designed to have a lot of excess flow capacity. However even with that excess capacity there are very specific reasons why the pickup screens on 1.8t engines are prone to clogging. (fig-17) More on this topic later in the troubleshooting section. The main issue with a clogged pickup screen is that you may not see a serious pressure drop at lower rpm's but at higher rpm's the engine may be starved for oil. However in this rpm range you would not necessary trigger a pressure warning. At higher rpm ranges the pump may try to draw more oil than then can pass through the clogged screen. In the most serious cases as the pump cavity forms the pressure inside of the chamber drops to a point where the oil actually boils this is called Cavitation. LINK
  
  
  
  
  
• Oil Pump Failure – Considering the simplicity of the Gerator oil pump failures are rare. Over time the clearance between the gear teeth and the clearance between the pump sidewalls will increase which will allow oil to slip past the pump cavities, thus reducing its efficiency and subsequent flow. This condition could be accelerated if oil is heavily contaminated with metal particles from engine damage, oil filter operating in bypass or extended oil change intervals. (fig-18-19) The reductions in pressure would be gradual. As noted previously pump wear can be accelerated due to cavitation as the small microscopic bubbles form in the pump chamber and quickly collapse. The forces are strong enough however to break down the surface of the pump gears and walls which causes pump wear. Mechanical failures could also occur such as broken chain, sprocket or sprocket key but these seem to be extremely rare.
  
  
  
  
  
  
• Excessive Bearing Wear – If you have no knowledge about how engine bearings work take a minute and read the interweb. Here is a brief starter LINK. The key thing to know is that engine bearings operate in a Hydrodynamic lubrication condition. Which means that a thin film or oil separates the rotating crankshaft from the bearing surface. Engine forces like the force of combustion pressure which are typically 550-650 psi push on the rods and the crankshaft with over 6500 lbs of force. The only thing that keeps the bearing surface of he rod bearing from smashing into the crankshaft bearing journal every engine rotation is this thin film of oil!
  
  What maintains that thin film of oil is a constant flow from the pump. In a properly working engine, as the crank journals rotate oil is forced from he bearing cavity but more oil is ready to fill the void immediately. If there is enough flow and pressure the bearing surface should never touch the crank.
  
  As with oil pump wear wear is something that normally occurs gradually over time. Most wear (perhaps 90%) occurs during the first few minutes of engine start-up when the bearing journals come into contact with the bearings before the oil is up to proper temperature (ie viscosity). Even the best cared for engines will be subject to progressive wear. As the clearance between the bearings and the journals increases the restrictions to flow decrease and so does the pressure. While the main bearings are usually the first to go, rod, cam and even turbo bearings can wear and reduce overall system pressure. What is interesting to note is that increased wear reduces flow, which further accelerates wear. Eventually reduce the flow the point where the bearing is totally destroyed (fig-20-21) LINK LINK
  
  
  
  
  
  
  
  
  
• Mechanical Engine Malfunction or Damage – Any element within the lubrication circuit can be broken or damaged and result in reduce system pressure. A damaged cam adjuster, or broken turbo thrust bearing would likely present other more obvious problems but they can none the less reduce flow and cause a low pressure situation. While also rare the pressure relief bypass valves in the oil pump and filter housing or even a piston oil jet could get stuck in an open or partially open position which would drastically reduce system pressure at the lower engine speeds.
  
  
• Clogged or Blocked Oil Passages - It is rather unlikely that the main oil supply passages could be clogged but it could happen to a severely abused engine subjected to long oil change intervals. Also there is one large drain tube through the cylinder head and block which drains back into the filter housing. You can see this in section 1. (fig-4) The size of this tube is sufficiently large enough where is should not impede the return flow of oil from the head but again if the engine has significant sludge buildup it could. If oil pumped to the cylinder head cannot drain back fast enough then the oil level in the pan can drop below the pickup tube and allow the pump to draw in air which will further reduce oil flow.
  

When trying to isolate the causes of low oil pressure and looking at this list it’s also important to note that many of these factors are interrelated such as oil temperature and viscosity. Also it’s very possible that an engine may have several causes of varying degrees which individually may not cause system pressure to fall below required levels, but combined have that result.



Section 6 – How the Oil Pressure Warning System Works

Before we move on, I need to say that this topic has been extensively and at time painstakingly explained many many times here on the Audizine forums. This section is really a copy and paste of some of those previous posts. Here are a few that I found and used when trying to diagnose my warning light problem. Thanks to walkey_talkey20 for explaining this many times. LINK LINK LINK LINK

The B5/B6 1.8t engines are equipped with a simple pressure switch connected to the oil filter housing after the filter. Refer back to (fig-2#17 and fig-7) The pressure sensor is a simply switch which is normally open. When the pressure reaches approximately 23psi the electrical contacts within the switch will close. One signal wire from the switch to the Instrument Cluster completes the monitoring circuit to ground when the switch is closed.

The oil pressure warning is triggered under certain conditions. The Instrument Cluster will signal a low pressure warning if any of the following conditions occur. The warning indicator on the dash will show a RED Oil Can. (fig-22) and you will hear three long beeps. This is not to be confused with the yellow sensor warning also shown, which is indicative of an oil level sensor failure and has nothing to do with the oil pressure.

• Condition 1 - If the switch is closed with the engine off a warning will be triggered
  
  This warning is designed to let the operator know that the switch is damaged, in that it is remaining in the closed position while no pressure is actually present, or the wire connecting the switch to the Gauge Cluster is shorting to ground. This type of switch failure can be confirmed by removing the switch and using an Ohm meter or continuity tester. If there is continuity between the switch connector prong and the threaded end of the sensor then the switch has failed.
  
  
• Condition 2 - If the coolant temperature is below 60º C AND the engine speed is greater than 300 RPM AND the oil pressure switch is open.
  
  This warning is designed to indicate that extremely low or no pressure exists while the engine is running. A healthy engine should have oil pressures well above the switch trigger limit of 1.4 to 1.6 bar (20.3-23.2 psi) Note: 70-100 PSI are common during startup. A disconnected switch, defective switch or broken wire to the Instrument Cluster would trigger this type of warning.
  
  
• Condition 3 - If the coolant temperature is above 60º C AND the engine speed is greater than 1500 RPM AND the switch is open for more than ½ Second
  
  This warning condition is designed to alert the driver that the pressure is too low during normal operating conditions. At 1500 RPM a healthy engine should be creating at least 30 PSI at 1500 RPM. If this specific condition occurs more than 3 times during continuous operation when warning will continue to stay active at any RPM

It's important to note that if you receive the warning light while driving and your engine speed is over 1500 rpm (Condition 3) you should consider this a serious situation. It is highly recommended that you stop the car safely and immediately and not drive it. Based on the repair history of this model, and Volkswagen/Audi Recalls for engine sludge problems, there is a strong likelihood that your engine indeed does have low oil pressure and this is not simply a broken wire or failing switch. While many people like myself have no idea what the warning means the first time they see it and do continue to drive you are risking causing more serious and permanent damage by doing so.


One more important warning. It is common for the pressure warning to come on between 1500-1800 rem where the pressure is operating close to the warning threshold. However, if you have the warning light while driving at highway speeds 2500 rpm or above then this means you engine is only pressure is dropping below switch threshold 17-23 psi when you should have about 40+. THIS IS A VERY SERIOUS CONDITION which if you continue to drive there is a very strong likelihood that you WILL cause permanent bearing damage.


Before we move on the the next section it is very important to note that the Oil Pressure Warning is NOT the problem it is the symptom of an underlying engine problem.




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Section 7 - Oil Pressure Testing and Specifications for the 1.8t (AMB)


So You Have Decided to Test Your Oil Pressure

Good! Hopefully by now you have received or borrowed an oil pressure test gauge kit. Amazon, Ebay, Harbor Freight are all good places to find one. Some auto parts stores will rent them as well. The key thing you have to check is to make sure the kit has the correct metric M10x1 adaptor. I recommend getting one with at least 6 ft of hose. I think it’s important to also test your pressure while driving and you won’t be able to do that if your tester does not have a long enough hose.





In addition to the pressure gauge and you basic set of wrenches and sockets you are going to need a 27mm socket to remove the oil pressure switch from the filter housing. It can be done with an adjustable or open end wrench but it’s a tight space around there.



Factory Oil Pressure Specifications

At this point before testing anything you need to know the proper pressure specifications.

• Oil (not coolant) must be at normal operating temperature 80°C
  
  
• Pressure at idling speed should be a minimum of 1.0 bar (14.5psi)
  
  
• Pressure at 3000 RPM should be between 3.5 to 4.5 bar (50 to 65psi)

Setting up the Test Gauge


If you are totally unfamiliar with your engine hooking up the test gauge is about as difficult as changing spark plugs.

• The oil pressure switch is located on the driver’s side of the engine. Remove the coolant reservoir and tilt it out of the way. Be carefully not to break the wire connecting the coolant sensor. You can unplug this if needed. (fig-25)
  
  
  
  
  
  
• It’s difficult to snap a photo of the switch because it’s obscured by some breather hoses, but it’s located on the right side of the filter housing facing the fire wall. (fig-26) There will be a single wire connector attached to it.
  
  
  
  
  
  
• Refer back to our diagram (fig-2#17) of the filter housing assembly and you are having trouble finding the switch. Also check out figure 7 as well. You can see the switch attached to the side in the photo.
  
  
  
  
  
  
• You will need to remove the electrical connector. Just like all of the Audi connector you will need a small flat head screwdriver to apply some force to the clip tab on the connector. There is not a lot of room and you cannot easily see the switch, so the first time you try this it’s takes a few minutes.
  
  
• After the connector is removed, use your 27mm socket to unthread the pressure switch. Have a small bucket or some rags ready because some oil will leak out.
  
  
• With the switch removed, now look at the fittings that came with your pressure test gauge setup. Find the one which looks like the threads on the pressure switch. By hand test fit this adaptor into the side of the filter housing. You should be able to thread this in without any resistance. The fitting on the housing is a NON-Tapered thread. If you use the wrong fitting for the test you will permanently damage your filter housing and you will NOT be able to put your original pressure switch back when your test is complete.
  
  
• Remove the fitting ant attach it to your gauge hose. Then thread the hose and fitting back into the filter housing. Use a wrench to tighten the fitting snug. You do not need to apply crazy torque here but it should be tight enough to limit the amount of oil leakage.

Conducting the Test

• Before staring up the engine, make sure you are in a well-ventilated place to work. You will need to rev the engine quite a bit during the testing so you want to avoid poisoning yourself with carbon-monoxide.
  
  
• Also before starting you should know that since your pressure switch is now disconnected in order to conduct the test you will receive the Oil Pressure Warning during the actual test. Just ignore it. (this time)
  
  
• Start the engine and check to make sure there are no obvious leaks from the filter housing or the hose assembly. If everything is connected correctly you should see a pressure reading on the gauge. If the engine is cold this might be 50-80psi. That’s normal and basically meaningless at this point.
  
  
• You will need to get the engine to operating temperature. The test specifications say that the oil temperature needs to be above 80° C. If you do not have a way of checking the temperature accurately I suggest letting the temperature gauge reach normal center position and then let the engine idle for 10 more minutes on a normal spring or summer day or longer in the winter.
  
  
• If you monitor the gauge while the engine is warming up you should see the pressure gradually fall as the oil heats up. This is also normal and basically meaningless at this point as well.
  
  
• Now once you are sure the engine is over 80° C you can start recording pressure readings.
  
  
• Make a table like this one to keep track of your results. (fig-26)
  
  
  
  
  
  
• First record the pressure at idle. Then increase the engine speed to 1000 rpm and record the result, do the same for 2000 rpm, and 3000 rpm. DON’T go to 4K or above yet. (fig-27)
  
  
  
  
  
  
• Compare your results to the pressure specifications. If you are at or above the minimum required pressures for the test to 3000 rpm it’s probably safe to test 4000 rpm and 6000 rpm. However if you find that you are not meeting the minimum pressure at 50psi at 3000 rpm there is really no point in going any further as you could risk further damaging your engine.
  
  
• Repeat the test from idle to 4K again. You should find that your readings have dropped slightly from the first test and again this is normal as the engine may not have been fully up to temp. These are the readings that count. If it’s safe to test 4000 rpm to 6000 rpm do so. Just remember DO NOT hold the engine at those high speeds for more than a second or two, max.
  
  
• If you find your pressure readings are marginal or just above the minimum it may be a good idea to test the pressure while driving. You’ll need someone to record the readings don’t try driving and writing while holding your gauge at the same time. What you may find is that your pressure readings differ significantly from your readings while parked. This information is important.
  
  
• If your test results show that your oil pressure is above spec, then try to recreate the conditions when you received the actual oil pressure warning as well. For example if you were stuck in bumper to bumper traffic and you got the warning when moving slowly, try to create that exact situation and note the pressure. Remember you are looking to confirm that your pressure is falling below the warning threshold and that could help explain the conditions causing the warning.

Continued on Page 4

[Toolaa]

Continued from page 3


Section 8 - Diagnosing and Troubleshooting Oil Pressure Problems

Troubleshooting oil pressure related problems can be challenging as there are so many components which could potentially impact oil pressure it’s simply not always possible to immediately pinpoint the source of the problem. Worse yet on older engines you may be dealing with several contributing factors causing low pressure. The best place to start is by ruling out the easiest and least expensive items first.
Before we start digging into your car we need a little history lesson.


Why does it seem that some 1.8t series motors seem so prone to oil pressure problems?

The 1.8t engine block that we see in B5 and B6 models has its roots going back to the original 1.8 non-turbo models from the mid 1980’s. In 1997 the first North American 1.8t model was the AEB engine. These were followed by the AWM and AMB models through 2005. For the most part this engine design proved to be most reliable and very well designed in many ways. The standard Oil Change interval recommended by Audi was every 5,000 miles. LINK


Starting around 2001 Audi dealers in North American (and Canada I believe) began to offer Care-Plus which was a service that new car buyers could pay for and it would cover all regular maintenance items, including Oil Changes. In 2002 the oil change service interval in the owner’s manual was changed to 10,000 miles. LINK (Some people presume to keep the service cost down) However it’s important to note that around the same time other manufacturers were also recommending extended oil change intervals to be more environmentally conscious.

After a few years it became apparent that a high number of 1.8t owners with longitudinally mounted engines in cars from 2001-2004 began reporting oil pressure warnings to dealers. It takes a while for engineers and statisticians to make sense of these repair trends but eventually patterns emerge. Someone figured out that a combination of factors was causing these engines to fail. The killer was sludge!





Turbocharged engines can generate a lot of heat near the compressor turbine. The turbo shaft bearing is a mere ¼” away from 900° temperatures. When turbo charged engines are driven hard it’s possible for the oil within the turbo to heat up to a point where it begins to breakdown and forms solid particles. This is especially true if an engine is shut down before the turbo can cool down, the oil in the turbocharger cooks and crystallizes. This cooked oil forms large particles which pass down into the sump and are then sucked into the pickup tube.

Coincidentally the longitudinally mounted 1.8t engines in the B5-B6 models had a smaller oil pan than their technically similar transverse mounted cousins. This smaller oil capacity made the engine more susceptible to overheating and sludge. Finally the straw that broke the camel’s back happened when Audi changed the oil change interval from 5K to 10K. This exacerbated the problem significantly. Combine this with the use of dino-oils, short trip/city driving, and the rest is history. . . And so were a lot of 1.8t engines.

In August of 2004 Audi agreed to settle a class action lawsuit which extended the engine warranty to 8 years (unlimited miles) for sludge related damages. (fig-29)





They also released in August 2004 Service Bulletin 170403 to dealers explaining what to do with customers reporting oil pressure warnings. This included the inspection, repair and even engine replacement procedures. This Service Bulletin was revised on 2008 to also include procedures to flush (de-sludge) engines, which had not yet experienced bearing damage. (see link in section 9)



Where to Start

The least expensive thing you can do to help diagnose you problem is know the repair history of your car. If you are the original owner then this will be easy. If not then you could try to find out the answers which could help rule out potential problems. If you are friendly with any Audi service tech’s try to ask them to look-up your vehicle service history. Some will be cool and give you a lot of information; others will not give you the time of day. At a minimum try see if you can determine if your car ever had a sludge cleaning by the dealer and if so how many miles ago. If you find a helpful tech you may be able to find out if the oil pump or filter housing have been replaced. Who knows, your car may have even had the engine replaced!



Identify Patterns which Cause the Low Pressure Warning

Obviously if the warning is occurring very often it may be too late, but if your warning light seems to be very infrequent chances are you are just beginning to approach the conditions where your engine could suffer serious damage and it may not be too late to save it from serious damage.


Try to remember or even record the state of operation when the warnings occur.

• Light acceleration at low RPM
• Heavy acceleration or high RPM
• Only on hot days
• Coasting
• During Engine Breaking

Then try to reproduce the warning. In my own case I realized that I only got a warning when driving slowly like in a parking lot. Usually it occurred right after a period of acceleration, then taking my foot of the gas for a split second and then gently accelerating again. Eventually I was able to recreate the conditions with a gauge connected. I drove around a empty parking lot with one foot on the gas and on the brake until I discovered if I revved to around 2200 then dropped back to 1000 and back up to around 1700 the pressure would lag around 18 psi for a split sec, which was enough to trigger the warning.



Troubleshooting Round 1


Troubleshooting oil pressure related problems can be challenging as there are so many components which could potentially impact oil pressure it’s simply not always possible to immediately pinpoint the source of the problem. Worse yet on older engines you may be dealing with several contributing factors causing low pressure. The best place to start is by ruling out the easiest and least expensive items first. Doing all of these first four items will cost less than $75.

• Change your oil - If you have not changed your oil in a while, start with some good quality synthetic 5w40 or 0w40 VAG approved oil (Here’s the list LINK) I'm sure some of you are just thinking why not dump thicker 15w50 oil in the car. We'll get to this a bit later, but for now, DO NOT change your oil to a heavier weight. Stick with approved oils.
  
  
• Choose a high quality oil filter - MANN 940/25 is an excellent filter LINK So is the MANN 950/4 as noted above (fig-16) LINK I found that during my own test there was about a 1 psi increase in post-filter pressure after switching to the much larger Mann Filter. While I don't know the physics behind the change I can only assume that the much larger filter area reduced the pressure loss across the filter media. The other point is that using my hand held gauge there is now way to know for sure if there was any real increase as 1 psi can easily be within the margin of error for the gauge. One thing for sure is that a higher quality and larger surely cannot hurt!
  
  
• Send out a sample of your old oil for a UOA - UOA = Used Oil Analysis. I've personally used Blackstone Labs LINK but there are other companies out there. You may learn some key details from the analysis which could impact oil pressure. as you compare your sample data against the data from thousands of samples for the same engine. (fig-31) For example. High levels of fuel dilution in your oil would reduce viscosity, High Copper, Tin or Aluminum levels could indicate excessive bearing wear. You can read more about UOA's and how to interpret the results here. LINK
  
  
  
  
  
  
• Test or replace your pressure switch - Obviously if you have already measured low pressure this is not going to do you any good. However if your pressure is good it may be the switch. If you have a small pressure regulator or leak down test kit and a electrical multi-meter or continuity tester, you can rig up your own switch test. (fig-31b)
  
  
  
  This photo is a test of my original pressure switch, which I replaced. However for this discussion I went back to test it just to see how it worked. After connecting it to the gauge and slowly increasing the air pressure the switch closed at exactly 20 psi. I repeated the test several times with exactly the same readings.
  
  While failures are rare they do happen from time to time and the part is fairly inexpensive, so it's easy to rule it out as a problem. P/N 06A919081J There are OEM models for less than $8.00. There are other very similar looking switches which operate at different pressures. There are suposed to be color coded, so be sure you get the correct model.

Troubleshooting Round 2


This next round of troubleshooting is going to require a little wrenching. Everything here can be tackled with a small toolbox and some basic repair knowledge.

• Check your Crankcase Ventilation System – You can disassemble many of the parts and simply clean them out, but if you engine is old it may be faster and easier to switch to the 034 Silicone Kit for $99. LINK A properly working breather system is going to make our car run better overall so you may consider this money well spent since it can improve performance and rule out one more potential source of oil pressure problems.
  
  
  It's also important to note that if you have excessively high crankcase pressures from piston ring wear and blow-by you can be masking actual low oil pressure problems in other areas. One way to confirm this would be to test you oil pressure with the oil fill cap both on and off at several different rpm speeds. A normal working engine would record no difference with the cap on or off. However if you pressure does drop with the cap off then you should assume you have other internal engine issues to eventually address.
  
  
• Inspect cam bearing cap(s) - If you did check out he link to the Audi service bulletin above you would notice that the procedure to determine if an engine was salvageable or should be replaced under warranty was to remove the font-most cam bearing caps and look for signs of oil starvation. Here is the example again from section 5 above.
  
  
  
  
  
  Why choose this one?
  
  We'll the front exhaust cam bearing cap, closet to the timing belt is actually the farthest component away from the oil pump in the engine oil circuit. So if you are having any serious low pressure/flow conditions your front cam bearings will begin to show signs of oil starvation and potentially fail before any of the other components. You will need to remove the valve cover, so be prepared to replace the gasket if it hasn't been done recently. If you do find signs of oil starvation then you have 100% confirmed that low oil flow/pressure is occurring or has occurred within your engine. Unfortunately there is no way to repair cam bearing damage the only repair option is to replace the head. However before deciding to spend that money, you are going to need to assess if you have main or rod bearing damage too before deciding to replace the head.
  
  
• Clogged or Blocked Oil Passages - Well while you have the valve cover off, take a minute to look around inside there. So you see any oil sludge. I'm not taking about a light film of black crud stuck to the underside of the Valve Cover; this is very common on engines with a lot of miles. Look actually on the top of the head around he lifters and bearing caps. If you see some goo with the consistency of fudge then you likely have and oil sludged engine. (fig-32) Assume that whatever crud is on the top end is also sitting in your oil pan, filter housing and everywhere else in the engine. However do not conclude that if the top end is clean so must the bottom end be cleaned.
  
  
  
  
  
  I highly recommend watching this video from the guys at Edge Motors where the show how they clean out a sludged engine. LINK
  
  
• Mechanical Engine Malfunction - This one is a little tougher to pin down, but let's cover the obvious things. For example if you know your turbo is dying or your cam adjuster is rattling like crazy these mechanical issues "Could" be impacting your oil pressure. Here is an example of a dying turbo with a blown oil shield, oil retaining ring and worn shaft which was blowing oil into the exhaust and at the same time likely blowing hot exhaust gasses into the oil flow.
  
  
  
  If you don't already have one I recommend spending a few bucks on a magnetic drain plug. It may not provide you with any immediate clues but in my case it eventually helped me confirm that something had gone wrong inside if my engine and that was what finally pushed me to take the next step. (fig-33b) I never found out conclusively where the metal fragments came from, nor do I know if the damage came from low oil pressure or was responsible for damage which caused low oil pressure. What I did know was that something was in my oil that wasn't supposed to be there!
  
  
  

Troubleshooting Round 3


Ok you've checked everything else and you still haven't found the cause of the low pressure. At this point be prepared to get your hands dirty, or pay someone else to do it. Everything else left to check is inside of the oil pan. Unfortunately getting inside there to inspect anything is a bit involved. I personally did not want to tackle this myself even as all signs were pointing me in the direction of a clogged pickup tube. I had the work priced out by a local Euro repair guy who quoted me $600 plus parts, which after doing myself I realized was a fair price. Yet still I didn't want to spend the money or do the work. I tried just about everything else I could think of like flushing the engine, adding cleaning products to the oil, taking off the oil level sensor to try and see inside of the pan (waste of time BTW), but in the end I realized that if I wanted to properly diagnose my problem I needed to get to the bottom of things. In this case it means the bottom of the engine!

• Clogged Pickup Screen - So we mentioned earlier that the pickup tube and screen assembly is designed to have about 15 times the open area as the main oil passage to the filter housing. It's totally normal for the screen to pick up small bits of broken plastic from the cam adjuster, oil chain tensioner, dipstick tube, as well as any other larger contaminants. If you look at the graph below (fig-34) and compare the amount of oil flow reduction as the screen becomes clogged to the engine flow requirements from Section 2 you will see what's happening here. At 6500 rpm the absolute minimum flow required is 50 l/min. When the screen is clogged about 90% you would still be able to flow 50 l/min. So you can conclude that even with a screen 90% clogged you can normally supply your engine with enough oil flow to run properly. However the pump's suction capacity is still higher than 50 l/min so with a 90% clog rate at higher rpm ranges the engine pressure may not be impacted but the pump can begin to cavitate as it attempts to draw more flow than the screen is capable of passing. This would begin to cause wear on the pump.
  
  
  
  
  Now look at the flow requirements over the entire rpm range. (fig-35) You can see that at 95% screen blockage the max flow drops to about 25 l/m. So at this level of blockage the engine may see enough oil at idle or even up to 2500 rpm which is still above the warning threshold, however flow will start to max out at 2500 rpm. At this point the pump will cavitate and the pressure will simply not increase at a linear rate or significantly at all.
  
  
  
  
  So even before removing the oil pan you may be able to determine if your pickup screen is clogged by carefully observing your oil pressure across the rpm range. If pressure is good at idle and lower rpm ranges but reaches a plateau between 3500 to 5000 rpm you could look more seriously at the pickup tube as a source of low pressure. I would like to point out that the physics behind liquid flow through a screen are also quite involved. I do not have the background or experience to calculate the exact effects. I did do some quick research to come up with a reasonable factor to use when calculating the flow. So please do not simply assume that if your screen only 70% clogged things will be fine. Just know that you lose flow as the screen clogs and at some point you may begin to cause excessive wear on the pump even before any other signs of low pressure occur.
  
  
  The best (and most direct) way to inspect the pickup tube is to drop the oil pan. It is quite a bit more involved and obviously not for everyone, but it's the only sure way to assess what's going on down there. Here's a link to a recent write-up on how to do that. LINK Also the video from Edge Motors linked above also shows how to drop the pan.
  
  I have read on other car forums where people have used a flexible USB camera scope like this LINK, to inspect internal parts of the engine. I have one that I used to inspect my intake valves on another car. It comes with a 90° Mirror adapter for the end. I am sure that you can feed the camera into the oil drain hole. The pickup tube is just above the drain hole. The quality of the images is very low resolution, but if he debris are significant they you should be able to see them in the camera. The next time I change my oil I will attempt to take some photos and post them here.
  
  
• Oil Pump Failure - As stated before oil pumps are very simple machines and in general are not prone to failure. However they can wear out over time. As the clearance between the gears increases the pump flow capacity decreases. You can use a simple feeler gauge to measure the clearance. (fig-36) I can give you my own example. After 165,000 miles I removed and inspected my own oil pump and there as a clearance between the gears of 0.101 to 0.120mm. I compared these numbers to my brand new pump which measured 0.76mm. I also rigged up a pressure test and compared both pumps under the same conditions. The new pump produced 30% higher pressure than the old pump. You can check out this test here. LINK
  
  (Disclaimer, I have no way of knowing how my simple test equates to actual engine pressure, the purpose was to simply see if there was any difference between my pump with 165,000 miles and a new one)
  
  
  
  
  One thing to note is that while a pump failure is very rare, replacing the pump is actually very easy once you have the oil pan off. The cost of the pump is around $110 for a genuine Audi replacement LINK If you are going through all of the trouble to drop the oil pan inspect or replace the pickup tube, you should seriously consider replacing the oil pump. I personally made this mistake and did not replace the pump the first time I dropped the pan. After I got everything back together I regretted that oversight as soon as I realized how much time went into getting the pan off. Unless you are on a very tight repair budget keep this in mind.
  
  
• Excessive Bearing Wear -
  
  The 1.8t main bearings are designed to have between 0.02mm and 0.04mm clearance within a new engine and the Audi spec allows for up to 0.055mm max clearance.
  
  As we mentioned before bearings are designed to wear over time. They are softer than the crank and made from low friction materials. When the crankshaft touches the bearing during start-up and sometimes briefly during heavy changes in acceleration or engine braking, microscopic bits of metal are scraped away from the bearing surface.
  
  There are some fairly complex formulas which are used to predict the amount of flow required for a journal bearing. (fig-39) However for our purposes, suffice it to say that as the gap between the bearing and the crankshaft widens there will be less resistance to flow. As this resistance decreases a higher volume of oil will need to flow through the bearing in order to provide the same load capacity. As the flow increases the pressure drops as less oil is available to fill the larger space.
  
  
  
  This chart shows data from a hypothetical bearing condition. You can see the relationship between the bearing clearance, flow and pressure required to maintain a fixed flow rate. What is striking is how quickly the pressure drops off as the clearance widens.
  
  
  
  So if you have exhausted all other troubleshooting avenues it may be time to check the clearance of your main and rod bearings. At this point in order to get to the bottom of your oil pressure problem you are going to need to get into the bottom of your engine! If you’ve removed your oil pan let’s assume you are fairly handy with a torque wrench and know your way around the engine. However consider that removing the bearing caps and reinstalling them without the proper guide can result in SERIOUS PERMANENT DAMAGE TO YOUR ENGINE!
  
  However before removing anything just look around at the bearing caps. If you see any metal flakes or shavings stuck to the crank or wedged between the cap and crank then you may be seeing pieces of deteriorating bearings. Also try to wiggle the rod ends. You should NOT be able to feel .050mm of clearance. So if there is any radial play then you have a problem.
  
  If you are confidant in your abilities then just make sure you have a set of 6 point ½” drive sockets and a high quality ½” drive torque wrench. With the removed you will be able to remove the caps on all rod bearings and main bearings 1 thru 4. The #5 cap may be able to be removed but I don’t think you can fit a socket on properly with the ream main seal attached. You need to know that the main bearing cap and rod bolts are single use TTY. If you remove them to inspect any bearings, you will need replacements. You can pick them up form ECS and others for about $3-$4 each. So expect to spend about $50 to inspect your bearings.
  
  Here are two examples from my engine. The first photo (fig-41) shows the #1 main bearing and crank journal. This checked out with 0.055mm clearance.
  
  
  
  
  This photo shows the #3 main bearing and journal. It’s obvious that the bearing damage is so severe that oil would have had very little resistance here and would have flowing at a very high rate, which would have reduced the available flow and pressure to the rest of the lubrication system. Yet for as bad as this looks the overall system pressure was holding at about 12.5 psi for quite a long time.
  
  
  
  
  

In the end the motor had to be pulled. All of the lower end bearings, seals and crank were replaced.
This engine survived….We’ll just need to see for how long…..



Continued on Page 5

[BerNur]

Great thread. I remember that light and the feeling.

[RENOxDECEPTION]

I like this.
Changed my oil pump recently, slight wear, no oil light, but a brand new CCT was ticking. It fixed my problem, and haven't heard the dreaded "diesel" sound as my friends called it since then.

[Toolaa]

Continued from Page 4

Section 9 - Additional Information and Wrap-Up [Time to Wrench!]

Hopefully this information has helped to enlighten you about how your engine lubrication system works, how to identify lubrication problems and perhaps even fix them yourself. If you are not a D.I.Y. person at the very least you should be able to have a meaningful and intelligent conversation with other forum members as well as your mechanic. If you are the D.I.Y type than I really do hope you are able to bring your car back to life and keep it running for a very long time. The B6 is a great car and I really enjoy driving mine which is all bone stock.


Hindsight is always 20/20

I would like to say that after wrestling with the low oil pressure problem for over a year I would like to reflect on some of the things I did wrong and what I would have done differently had I known better.

First after I brought the car I could have taken it back to the seller after a few days. He explained that if I was dissatisfied for any reason. If I'm ever in a situation like this again the first thing I would do when I get home is a compression test, leak-down test and oil pressure test. In my case I would have known right away the baseline condition of the engine. Had I done this I might have taken the car back and purchased a better A4! Lets call this Mistake #1

I should have taken the car to the dealer where it was purchased and serviced for 9 years and introduced myself as the new owner. I would have paid for an oil and filter change and asked them their opinion on the car. Knowing that they would likely want to sell me as much of their service time as possible I would have tried to get as much service history from them as I could. I'm sure they would have looked in the computer and gladly stated "Hey did you know that you car is due for a timing belt service. Can we give you an estimate" I would have said "Sure! You guys are great what else is it due for?" I eventually got some of this information but I think it would have been easier to do it right way.

After the first time I got the Pressure Warning I called a local tech. I could hear in his voice the hesitation and I knew he didn't want to go into a long explanation about how it could be dozens of things. He did tell me right away that these engines were prone to sludge problems and that over time restrictions to the lubrication system could damage the bearings. He would charge me $600 to drop the pan and replace the pickup tube. I didn't know any better but I was hesitant to drop that kind of coin without knowing more. However he was totally right about what needed to be done.

So I read, read, read and then read some more about sludge. Then I came to a brilliant conclusion that all of my problems could be solved by using Auto-RX! Lets call this Big Mistake #2

I promptly ordered two bottles of this wonder liquid and began to follow the instructions. About 2 days after using Auto-RX I was driving I was accelerating up a hill and at about 3-4K rpm my engine stuttered hard and a huge puff of smoke bellowed out of the exhaust. This happened 2 or three times again within about two weeks. I began to notice a few more frequent pressure warnings too. About this time I figured out that I needed to do my own pressure test. The results were pretty low.

I decided to drain the oil with the Auto-RX and switch to Rotella-T6. While draining the oil I found those pieces of metal in my pan and shortly thereafter it became apparent that my turbo was dying.

I really cannot prove that Auto-RX had any positive or negative impact on my engine, but I do believe that it significantly reduced the oil viscosity. Considering that my engine had 155K miles at the time, that lower viscosity couldn't have helped operating conditions inside of the motor. After going to 5w40 oil I did see a minor improvement in pressure.

I replaced the turbo, tons of breather components, cam adjuster and the car began to run great. The oil pressure went up again slightly to just barely below spec at idle, but I still received the occasional warning light. So after exhausting all possibilities I was faced with dropping the pan and checking the pickup tube.

When I dropped the pan I found that things were almost clean. Way too clean. I didn't realize it at the time but the car had obviously had the sludge treatment done by the dealer at some time. I did find some plastic bits in the pan and even some metallic flakes. I assumed these were from the turbo failure. This was Big Mistake #3. The fact that they were still floating in the bottom of the pan and not wedged into the screen should have also indicated to me that the problem was still happening. I had less than 500 miles on that oil. It's obvious now that those metal shavings were from my failed or failing #3 bearing.

After cleaning out the pan and replacing the pickup tube anyway, even though it didn't really look clogged, I bolted everything back together. I guess I figured there really wasn't any more I could do at that point. This was Mistake #4. There was plenty I should have done with the pan off as I've noted above. At a very minimum I should have replaced the oil pump. While the pressure improved to about 13.5 psi at idle, but it was still just below spec.

In hindsight I should have looked at the main bearings. I would have discovered my problem 9 months earlier.


Why not use heavier weight oil to solve low pressure problems?

I guess this is a good question. If higher viscosity oil increases resistance to flow then it will also increase oil pressure within the system. So if you want to keep you oil pressure light from coming on then using higher viscosity oil like 15w50 will achieve that goal.

Hello McFly...... Increasing resistance to flow = less flow!!!





If you have not learned this by now then all I can say is good luck...


Additional Information and Information Sources

Audizine - Obviously the community has been a big help. There really is no way that I would have attempted to tackle any of these problems on my own without this great resource. I know that many times I felt like nobody was listening to my request for help, but I learned real quick that to get help you need to be willing to give clear and concise information about your problem and show potential helpers that you care enough about your own problem to be willing to take the time to do your own research and provide accurate follow-up information. So if you are new to Audizine or Forums in general take this comment seriously.

Automobile Related

www.passatworld.com - There is a good user group there and you will find some great forum discussions about B6's and 1.8t's

www.vwvortex.com - Good community over there too, but there are so many models that the B6 support seems to get lost in the mix.

www.ericthecarguy.com - Great auto repair guides and videos for beginners - I want this dude's job!

www.aa1car.com - Good site to learn about how car systems work in general and how to diagnose general problems

www.vagcat.com - Looking for parts diagrams and numbers this is the place. Show me one better and I'll post it here.

www.enginebuildermag.com - Good general information about repairing and building engines

www.bitog.com - If you want to know about oil this is the place - Trust me, you have no idea how much there is to discuss about oil!

www.workshop-manuals.com/audi - Online Audi Repair Manuals - If anything this will convince you to actually invest in the Bentley manual. Here is the link to the Sludge TSB Noted in Section 8 LINK and the Class Action Lawsuit Settlement Details LINK


Engineering Related

www.freestudy.co.uk - Engineering resources formulas related to fluid dynamics - Helped me remember stuff from my collage days that has been long since forgotten

www.subtech.com - Highly technical information about substances and materials good information about lubrication and bearings LINK

www.saedigitallibrary.org - Really want to learn something about automobile engineering read some of these technical papers - Some are free but most cost about $20

Controlling Positive Displacement Pumps - Short web page with some good charts showing how pressure curves of PD Pumps

Waukesha Pumps - Engineering Manual (PDF) - While these pumps are not for automotive engines, the information in this manual is very informative and relates directly to how the gerator pumps in our cars work.

Bearing Design In Machinery - If you have an engineering background and you get turned on when you see formulas with a lot of Greek letters like Δt Q³ ξ then read this. I checked it out from the library and I realized that I haven't used these parts of my brain since the first George Bush was president.


Other Sites

www.shw.de/cms/en/ - SHW AG is the designer and original OEM for the Oil Pump VAG P/N: 06A115105 - LINK Here is a PDF power point presentation showing a photo of the pump in a shareholder presentation one interesting thing to note they reference the cost of standard oil pump at 12 euro.

www.machinerylubrication.com - Great site for general information lubrication. Good article explaining oil filter efficiency and Beta Ratios LINK

www.minimopar.net/oilfilters/german.html - This guy has been, dissecting and studying oil filters including a few German brands compatible with 1.8t

Ford SHO Club Again good breakdown on oil pressure and lubrication specific to Ford SHO engine, but none the less useful






Revision History

08/16/14 - Correction to Section 6 - Thanks Walkey_Talkey20
08/17/14 - Updated Section 5 to include correct oil filter specifications
08/17/14 - Correction to several sections and photos Oil Gallery spelled incorrectly LINK - Thanks diagnosticator
08/17/14 - Added some of the missing web links to Section 9
08/17/14 - Added Oil Pressure Switch testing


Almost DONE.......

[SlickFix]

Wow, just wow. You have gone above and beyond with this thread, Toolaa. Awesome stuff!

How do you feel about doing one for the 3.0 engine?

[Knives1010]

This thread right here is one of the reasons this community is so great.

[whitedog]

OK, I'm going to bookmark this to read through another day. It's way past beer-thirty here, but this looks like a definite good read and should be put someplace important.

[boy412]

Thanks for putting all this together. Great post! Lots of great information here...

[DiertyEuroSpec]

I fucking love this! Toolaa serious props and now going to see if you have anymore write ups which seem like they are worth their weight in gold! Bad analogy but you get the point.

[Toolaa]

I wrote up an Oil pan removal DIY which was really a rehash of other good post but with some missing details and broken links.

Old Guy recently replaced his K03 with a new one and I had a G-Pop rebuild kit sitting in my garage collecting dust. Fletcher gave me his old K03 and I promised to rebuild it and post the DIY here. It will get done. I've just been so busy with my business that I cant seem to get a nice break to do it. However, i consider the quiet time doing repairs like this really relaxing so maybe I need to make the time to chill and get it done.

PS I need to do some spelling and grammar edits to this guide. I'll get those done too. Also I am looking for real world oil pressure data which I will use to add more info to this thread. If you have a way of collecting oil pressure results please post them here.

http://www.audizine.com/forum/showthread.php?t=611523

Thanks.


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[Charles.waite]

Wow. Epic guide. I need to file this away as my b7 2.0t is experiencing some oil system related issues. I know that engine is a bit different, but still lots of awesome information here as i'm pretty sure the oil routing through the block and head is nearly the same.

[Toolaa]

Charles thanks for the comments. Sorry to hear about your possible Oil pressure troubles. I think you are correct about the oil flow for the 2.0FSI being similar to the 1.8t. I remember reading that USP sells an oil pump conversion kit for the 2.0 to install a standard AMB pump.

http://www.uspmotorsports.com/USP-FS...5&partner=8673


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[C4.Style]

Great Stuff, just found this thread. But I have quite an issue with the pressure switch. The oil seems to leak straight through the switch it self which causes then to drop oil on the cooler and make its way down on the ground. We replaced it with a new switch. It was fine for about 200 miles and now again there is a leak, same thing through the switch. Any idea why? or where to start? Prior to this, we installed new Oil Cooler+O ring.

[RENOxDECEPTION]

if it leaks through the switch then obviously you need an oem switch?
also, you bumped a thread from 2014 with an unrelated topic, make a new thread.

[aluthman]

Currently researching an 06A pump conversion for my 2.0 FSI and this thread helped a lot with understanding the 1.8T oiling system. Thanks!

[areknee]

Hi, thanks for this write up. I got the oil pressure light driving on the highway, thinking it was a low oil light I kept driving and put more oil in when I got back home. Drove the next day and the light came back on and it sounded like a diesel lawn mower. Took it to get seen and they said it was most likely the timing chain and that the tensioners where not getting oil and it was jumping time, they said they would do more tests but I was looking to a couple grand of work. I drove a few blocks home and now I'm thinking maybe I don't want to scrap it.

From what I see here it doesn't seem to be sludge, timing belt has low tension don't know if that is normal and the chain seems to be half a notch out of time. Before I replace the CCT and drop the pan, how do I check if I need to repair the head or if the entire block is scrap? To be honest I thought the red oil light meant low oil






Thanks!

[areknee]

I took the some of the top bearings off, the ones showed in the picture above today. I thought it was a torx 30 and got the first one off then I stripped like three screws following that. I've been trying to find a T35 but am now gonna end up ordering it online with an engine support bar.

The two bearings I took out looked fine, once I get the bar and I can look under I will check the ones on the bottom side. I have the tool to remove the head bolts, should I be checking for broken valves before proceeding? How long of a process is it to pull the heads? Do I need to take the belt and manifold off?

Also I counted 15 rods on the timing chain between the two cam shafts arrows does mean I need to do something to fix the timing or when I get oil pressure back hopefully after clearing the pick up screen and checking the oil pump can I expect it to fix itself now that it can get oil pressure?

Thanks for the help.

[davkav]

I think you need to slow down with your analysis....

You got the low oil light (yellow) and not the low oil pressure (red) so you may not have starved the engine of oil.

I dont think the Chain tensioner can retract far enough to allow it to jump a tooth, I could be wrong though.

Was there definitely a significant change in sound of the engine running?

[areknee]

I had the red oil light on my digital screen, I thought it was the low oil light because I would think the low oil pressure light would have shown on the cluster and not on the screen so I pulled over and added oil and kept driving (probably too much oil now), that cam chain diesel/lawn mower sound came shortly after and went away when I drove at a high RPM for a short period of time. 10 minutes later CEL light came on turned the car off, the code was for the timing being over retarded and a knock sensor. I just ordered the support bar and other things needed for looking at the oil pick up so hopefully I didn't trash my engine.

[old guy]

The cam timing code probably occurred because there wasn't adequate oil pressure to activate the cam chain adjuster. The knock sensor as probably set off by the cam adjuster rattle. I would recommend pulling one or more of the bearing caps while you have the oil pan off and check for galling.

[Jakal]

So my oil light has been coming on after around 17-25 miles of consistent driving. Mostly highway/freeway driving. Would this be oil pressure?

[fR3ZNO]

Flow (Q) = Velocity (V) x Area (A) x Time (t)

Awesome write up, and a good read. Tickles my mechanical engineering fancy.

However, just an FYI this flow equation is incorrect. The units don't work. Assuming you're talking about volumetric flow, the units are (volume/time).

[Flow (Q) = Velocity (length/time) x Area (length^2) x Time] reduces to: [Flow (Q) = length^3] when it should be:

[Flow (Q) = Velocity (length/time) x Area (length^2)] = [Flow (Q) = length^3/time (volume/time)]

So you simply drop the time at the end of your original equation.

[DasWagen]

So my oil pressure light never comes on, even with my sensor unplugged. The sensor functions as intended and the supply wire get 12V w/ the engine on, but the instrument cluster says OK no matter what.

I have no idea what to do about it

[Chericon]

Why cant i view the figures in this post?

[RobGuadalajara]

This is an amazing thread. There are few photos missing. I want to know where the oil check valve in that keeps oil in the valve train when the engine is not running. How much work is it to check it and replace it? I have a newly rebuilt long block that I was unable to supervise the rebuilding closely. The engine is noisy on startup for 1 - 2 seconds. I suspect it's the tappets oiling up. Thanks.

[Toolaa]

This is an amazing thread. There are few photos missing. I want to know where the oil check valve in that keeps oil in the valve train when the engine is not running. How much work is it to check it and replace it? I have a newly rebuilt long block that I was unable to supervise the rebuilding closely. The engine is noisy on startup for 1 - 2 seconds. I suspect it's the tappets oiling up. Thanks.

It’s been a long time since I’ve posted here. The check valve for the 1.8T is actually located within the oil filter itself. Many modern filters have built in check valves. My first suggestion would be to just make sure you are using the correct filter type.


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[artix77]

Hi! I have read all of this post and I must say you did an amazing job. Thank you very much. I have seen you still answering this post and I am really running out of options so I thought I would try to ask You here.
I am owner of Skoda Octavia mk1 1.8t AUM 150 HP. I didnt really know much about cars before but now I had to learn quick...I am not fixing it myself tho. I gave car to mechanic. I have been fighting with oil pressure problem for some time now and I am slowly hopeless.
So I originally had problem couple months after I get this car from my Dad who didnt take care of it very well. I didnt know it at that time. It is my first car btw. So while driving on highway (right next to home)suddenly I see red engine oil pressure warning. Stupidly I drive very slowly 3km to home.
Next day car go to mechanic, he told me oil pick up tube was clogged from sludge which stop oil going compeltly. There was worry about parts of enginge being damaged so he checked main bearings as well as pull out turbo to check it inside. Luckily there was no severe damage according to him, although he found metal parts in sump. He replaced oil pick up tube.
There was a lot of sludge in the enginge. So he recomended doing engine flush. He put new oil as well as far as I know it was castrol edge 5w40. He told me to come change engine oil again after 2000 km to prevent dirt blocking oil pickup tube cuz there might be more dirt coming out. For this 2000 km eveyrthing was perfect dreaded low oil pressure light naver came on.
So I went to change oil after 2000km. They change for same oil. 2 days after oil pressure light coming on... I imidietly stop the car. Didnt want to risk damaging anything so I called tow truck. Car went to same mechanic. He said there is no control, he messured pressure and its all good. Weird....
Since then oil pressure light comes on sometimes for like 2 second and then it goes off. It always happen on low rpm/low speed (around 1000-1800 rpm and 20-50 speed). It never come on over that speed/rpm. I literally drove on highway for 1 hour, stoped to take piss and smoke ciggi went back to car drive from parking and before I even drive from parking light could go on for a second and then I drive on highway again for 2 hrs and nothing happen.
Oil pressure light keep coming more often and going off, then it start turning on and the only way to turn it off was to turn off the enging, after you turn it back on there was no control. It started to popping very often tho every 1-2 min (engine sound completly fine, no loss of power etc.) So I took tow truck again to mechanic to not damage the car. Now my car is in mechanic again... Oil pan down again, there was some metal bits not too much he said they might befrom oil pump, he checked and clean oil pick up tube (that wasnt a problem), he changed oil pump as well as oil pressure sensor itself.
Problem was still happening. He put new oil filter and change oil cooler as well. He drove it and said it's still hapening. Well he mentioned it happend only once but still. Mechanic starting to tell me he doesnt really know what else could it be. Tomorrow he is gonna have a look on oil filter housing and check Pressure Relief Bypass Valve. He told me this is his last idea.
I literally dont know what to do anymore. After reading your article I start to think it might be main bearing which is causing it but mechanic keep telling me he checked them (i literally asked him 5 times about this). Knowing all this information do you possibly have any idea what could be causing those drops of pressure? Sorry for my English its not my main language. Please let me know if you need more information from me or have any idea.

[Toolaa]

Hi! I have read all of this post and I must say you did an amazing job. Thank you very much. I have seen you still answering this post and I am really running out of options so I thought I would try to ask You here.
I am owner of Skoda Octavia mk1 1.8t AUM 150 HP. I didnt really know much about cars before but now I had to learn quick...I am not fixing it myself tho. I gave car to mechanic. I have been fighting with oil pressure problem for some time now and I am slowly hopeless.
So I originally had problem couple months after I get this car from my Dad who didnt take care of it very well. I didnt know it at that time. It is my first car btw. So while driving on highway (right next to home)suddenly I see red engine oil pressure warning. Stupidly I drive very slowly 3km to home.
Next day car go to mechanic, he told me oil pick up tube was clogged from sludge which stop oil going compeltly. There was worry about parts of enginge being damaged so he checked main bearings as well as pull out turbo to check it inside. Luckily there was no severe damage according to him, although he found metal parts in sump. He replaced oil pick up tube.
There was a lot of sludge in the enginge. So he recomended doing engine flush. He put new oil as well as far as I know it was castrol edge 5w40. He told me to come change engine oil again after 2000 km to prevent dirt blocking oil pickup tube cuz there might be more dirt coming out. For this 2000 km eveyrthing was perfect dreaded low oil pressure light naver came on.
So I went to change oil after 2000km. They change for same oil. 2 days after oil pressure light coming on... I imidietly stop the car. Didnt want to risk damaging anything so I called tow truck. Car went to same mechanic. He said there is no control, he messured pressure and its all good. Weird....
Since then oil pressure light comes on sometimes for like 2 second and then it goes off. It always happen on low rpm/low speed (around 1000-1800 rpm and 20-50 speed). It never come on over that speed/rpm. I literally drove on highway for 1 hour, stoped to take piss and smoke ciggi went back to car drive from parking and before I even drive from parking light could go on for a second and then I drive on highway again for 2 hrs and nothing happen.
Oil pressure light keep coming more often and going off, then it start turning on and the only way to turn it off was to turn off the enging, after you turn it back on there was no control. It started to popping very often tho every 1-2 min (engine sound completly fine, no loss of power etc.) So I took tow truck again to mechanic to not damage the car. Now my car is in mechanic again... Oil pan down again, there was some metal bits not too much he said they might befrom oil pump, he checked and clean oil pick up tube (that wasnt a problem), he changed oil pump as well as oil pressure sensor itself.
Problem was still happening. He put new oil filter and change oil cooler as well. He drove it and said it's still hapening. Well he mentioned it happend only once but still. Mechanic starting to tell me he doesnt really know what else could it be. Tomorrow he is gonna have a look on oil filter housing and check Pressure Relief Bypass Valve. He told me this is his last idea.
I literally dont know what to do anymore. After reading your article I start to think it might be main bearing which is causing it but mechanic keep telling me he checked them (i literally asked him 5 times about this). Knowing all this information do you possibly have any idea what could be causing those drops of pressure? Sorry for my English its not my main language. Please let me know if you need more information from me or have any idea.

I’m sorry to hear about all of the troubles. It sounds like your mechanic is changing all of the likely problem parts. However the metal shavings he is finding inside of the oil pan are troublesome.

I’m going to suggest that he connect an actual pressure gauge to the engine with a hose long enough to monitor the gauge while driving. Then he can see of the pressure is dropping only under specific conditions. If the pressure is within specifications and the light is still turning on, it would indicate a problem with the switch circuit.

However, if they are finding low pressure at idle, and also below specifications while driving at higher RPM, I suspect the problem is actually with the crank bearings. I know you said the previous mechanic checked them, but unless he removed all of the bearings and the crank there really is no way he could be sure they were not worn out.


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