Oil pressure light, but oil pressure is fine...?

[syrinx32123]

Here's my situation

- Was getting the "low oil pressure" warning light intermittently. Usually at RPMS less than 2000.

- Brought my car into the shop and had the oil pressure checked with a mechanical gauge. The mechanic said it was fine. ($200)

- After the car got out of the shop, the light didn't come on for about 2 weeks. It's fixed!

- But then yesterday it started coming back on intermittently at RPMs less than 2000.

This leads me to think it must have something to do with the switch or sensor?…
When the mechanic checked the pressure, did he tighten something that made the reading more accurate?

Any ideas?

2000 A4 B5 1.8T Quattro Avant
120xxx miles

[Euromike]

Very common thing with the B5 1.8T's is the oil pump getting gummed up with engine sludge and failing.

Drop your oil pan, check your pick up screen. Look for sludge.

[syrinx32123]

Very common thing with the B5 1.8T's is the oil pump getting gummed up with engine sludge and failing.

Drop your oil pan, check your pick up screen. Look for sludge.

Yes but the when the mechanic checked the pressure with a gauge, he said it was normal. Could it be a failed oil switch? Also, I'm thinking of using Auto RX to clean out any sludge just in case.

[Euromike]

Where did you take the car? Does the mechanic know what normal is for a 1.8T?

Never heard of the oil switch failing intermittently like that. When it fails, it usually fails.

Really thinking clogged or bad oil pump.

[walky_talky20]

It can be the switch. A failed switch can cause cluster warning behavior very similar to a real low oil pressure problem.

Your mechanic charged $200 to check the oil pressure?! It takes 15 minutes to do it. And 10 of those minutes are just finding the oil pressure gauge kit in the back of the tool box. I, for one, am not willing to take his word for it that the pressure is "fine". I would want to see the actual values. And geez, for $200 he should give you a detailed color graph of pressure vs RPM with separate curves based on oil temp.

In any case, the magic number here is 1500 rpm. When the car is warm (coolant temp over 60C), that is the rpm at which the cluster expects the switch to be closed. That means it can require up to 23psi by 1500 rpm. So I'd want to see pressure numbers for idle, 1500 rpm, 2k, 3k, 4k, and 5k with oil temp at 200F+.

[syrinx32123]

It can be the switch. A failed switch can cause cluster warning behavior very similar to a real low oil pressure problem.

Your mechanic charged $200 to check the oil pressure?! It takes 15 minutes to do it. And 10 of those minutes are just finding the oil pressure gauge kit in the back of the tool box. I, for one, am not willing to take his word for it that the pressure is "fine". I would want to see the actual values. And geez, for $200 he should give you a detailed color graph of pressure vs RPM with separate curves based on oil temp.

In any case, the magic number here is 1500 rpm. When the car is warm (coolant temp over 60C), that is the rpm at which the cluster expects the switch to be closed. That means it can require up to 23psi by 1500 rpm. So I'd want to see pressure numbers for idle, 1500 rpm, 2k, 3k, 4k, and 5k with oil temp at 200F+.

It was a German car specialist and his labor is $135 an hour. I thought it was very expensive too. He said it was at 15 psi at idle, and 37 psi at 3000 RPM

I don't have the $$ to drop the pan to clean the pickup, so I was thinking about using Auto RX. Has anyone tried this?

[skim464]

hooking up an after market oil pressure gauge isnt a hard job and also cleaning the oil pan isnt a hard job either it just would take an oil change(guess it will cost some $$) but yeah be sure to check oil pressure with an after market oil pressure gauge and leave it in the car, it will save you $$ if anything ever happens to ur oil pump

Your reading should be

Idle - 1-2.5 bar (14-36 psi)

3000 RPM - 3-5 bar (44-73 psi)

Disclaimer: These readings is for Audi A4 2.8 Quattro, but it should be a fairly good guide line for 4 cylinder A4 as well

Do what Walky_Talky20 said and take reading at idle, 1500, 2k,3k,4k,5k at operating temperature, also noting the oil pressure on start up and cold drive. It should almost never fell below the minimum pressure. If your oil pressure is barely meeting the specification when engine is COLD -> You will need to do a further research to address the issue as rising temperature only reduces the pressure (Correct me if I am wrong)

[M-Hood]

It was a German car specialist and his labor is $135 an hour. I thought it was very expensive too. He said it was at 15 psi at idle, and 37 psi at 3000 RPM

I don't have the $$ to drop the pan to clean the pickup, so I was thinking about using Auto RX. Has anyone tried this?

15psi is too low for idle which is most likely why you keep getting a light. Your oil pressure at idle with the engine at running temps should be around 25psi.

What weight oil are you running? Running too thin of an oil can cause low oil pressure, worn bearings can also cause an increase in flow which can cause a decrease in oil pressure. You can try putting in a thicker oil to see if the pressure comes up and the light stops coming on.

[syrinx32123]

hooking up an after market oil pressure gauge isnt a hard job and also cleaning the oil pan isnt a hard job either it just would take an oil change(guess it will cost some $$) but yeah be sure to check oil pressure with an after market oil pressure gauge and leave it in the car, it will save you $$ if anything ever happens to ur oil pump

Your reading should be

Idle - 1-2.5 bar (14-36 psi)



3000 RPM - 3-5 bar (44-73 psi)

Disclaimer: These readings is for Audi A4 2.8 Quattro, but it should be a fairly good guide line for 4 cylinder A4 as well

Do what Walky_Talky20 said and take reading at idle, 1500, 2k,3k,4k,5k at operating temperature, also noting the oil pressure on start up and cold drive. It should almost never fell below the minimum pressure. If your oil pressure is barely meeting the specification when engine is COLD -> You will need to do a further research to address the issue as rising temperature only reduces the pressure (Correct me if I am wrong)

Thanks for this info! I will look into installing an aftermarket gauge. Do you know of any DIY manuals on the internet for this?

[syrinx32123]

15psi is too low for idle which is most likely why you keep getting a light. Your oil pressure at idle with the engine at running temps should be around 25psi.

What weight oil are you running? Running too thin of an oil can cause low oil pressure, worn bearings can also cause an increase in flow which can cause a decrease in oil pressure. You can try putting in a thicker oil to see if the pressure comes up and the light stops coming on.

Sorry, I'm a bit of a car newbie. This is the first car I have ever owned. What bearings are you referring to? Also, how do I know that weight of the oil? I'm using Pennzoil Ultra Euro 5W-40 Full Synthetic with a Fram Oil Filter. Is the weight the 40 part?

[ricekikr]

Check the wiring on the oil pressure switch. Might've simply gotten loose. Happened to me once. This would also explain why it happens intermittently.

[syrinx32123]

Check the wiring on the oil pressure switch. Might've simply gotten loose. Happened to me once. This would also explain why it happens intermittently.

can you post a photo of where I could find the oil switch?

[nemick]

I run Mobil 10-40 high mileage oil. Give that a try.

[M-Hood]

Sorry, I'm a bit of a car newbie. This is the first car I have ever owned. What bearings are you referring to? Also, how do I know that weight of the oil? I'm using Pennzoil Ultra Euro 5W-40 Full Synthetic with a Fram Oil Filter. Is the weight the 40 part?

rod bearings and main bearings. As they wear the gap between them and the parts they are connected to becomes larger and that allows oil to flow thru it easier and this in turn decrease oil pressure.

can you post a photo of where I could find the oil switch?

Oil pressure sensor is near your oil filter which is located just below the back of your intake manifold.

[walky_talky20]

He said it was at 15 psi at idle, and 37 psi at 3000 RPM

Those are very decent values if you drive a Camry. Not so much for a 1.8T.

Pretty sure this is your problem. Firstly it's *barely* meeting spec at idle (minimum spec for hot idle is 14.5psi). And the measurement at 3000 RPM is not even meeting spec (should be 50-65psi). And even "spec" is below normal values for a healthy 1.8T. My 1.8T is never below 24psi at idle and gives 75 psi at 3000 RPM. These measurements are with oil temp above 200F. I cruise on the highway at 3500 RPM and it holds at 80 psi, all day.

I'm pretty sure your pickup tube is about 3/4 clogged up.

[syrinx32123]

Those are very decent values if you drive a Camry. Not so much for a 1.8T.

Pretty sure this is your problem. Firstly it's *barely* meeting spec at idle (minimum spec for hot idle is 14.5psi). And the measurement at 3000 RPM is not even meeting spec (should be 50-65psi). And even "spec" is below normal values for a healthy 1.8T. My 1.8T is never below 24psi at idle and gives 75 psi at 3000 RPM. These measurements are with oil temp above 200F. I cruise on the highway at 3500 RPM and it holds at 80 psi, all day.

I'm pretty sure your pickup tube is about 3/4 clogged up.

Do you think Seafoam or Auto RX will take care of this? I really cannot afford to drop the pan to get to the pickup

[nunya]

Those are very decent values if you drive a Camry. Not so much for a 1.8T.

Pretty sure this is your problem. Firstly it's *barely* meeting spec at idle (minimum spec for hot idle is 14.5psi). And the measurement at 3000 RPM is not even meeting spec (should be 50-65psi). And even "spec" is below normal values for a healthy 1.8T. My 1.8T is never below 24psi at idle and gives 75 psi at 3000 RPM. These measurements are with oil temp above 200F. I cruise on the highway at 3500 RPM and it holds at 80 psi, all day.

I'm pretty sure your pickup tube is about 3/4 clogged up.

Threads like this always worry me. Mine is ~10-14psi at idle, hot. I have mentioned it to 034 and they assure me its fine. I do have an external oil cooler etc, and did a T where the stock sensor is for the PLX sensor. I never get a pressure light.

--dillon

[skim464]

Well my car always had low oil pressure because when it was rebuilt 30,000 miles ago, oil pump was not replaced and i think it is getting weak... but my friend had to take the engine out to do a pressure plate work(it broke) and after that job, oil pressure reading increased to meeting the spec (still on a lower side but within the value) I think the connection was just getting loose and it is possible that could cause faulty pressure light. Check the connection and clean it up if it is dirty

[thenj3]

Threads like this always worry me. Mine is ~10-14psi at idle, hot. I have mentioned it to 034 and they assure me its fine. I do have an external oil cooler etc, and did a T where the stock sensor is for the PLX sensor. I never get a pressure light.

--dillon

Mine are about the same. I've always been cautious. It started happening right as the weather got hotter but then I put my car away. I run 10-40 oil might go up to 50 next summer. What oil do you run

[nunya]

Mine are about the same. I've always been cautious. It started happening right as the weather got hotter but then I put my car away. I run 10-40 oil might go up to 50 next summer. What oil do you run

5W-40 Pentosin

http://www.034motorsport.com/fluids-...ers-p-767.html

--dillon

[M-Hood]

Threads like this always worry me. Mine is ~10-14psi at idle, hot. I have mentioned it to 034 and they assure me its fine. I do have an external oil cooler etc, and did a T where the stock sensor is for the PLX sensor. I never get a pressure light.

--dillon

Did you have any work done to your crank or end up going with plus clearance bearings? I know 1.8t owners that went plus clearance bearings and others that had their crank polished, all of them ended up having oil pressure around 10-15psi, then to find out that they needed to run a thicker oil like 15w50 with those setups to get the oil pressure where it needed to be.

[walky_talky20]

Do you think Seafoam or Auto RX will take care of this? I really cannot afford to drop the pan to get to the pickup

I would not suggest a cleaner product at this stage. If the screen is clogged and it needs cleaned out. Yes, some people have had success getting the pressure back up a bit with flush/cleaner products. One guy on here made a little scraper device to go in the oil drain plug hole and touch the screen.

From what I have experienced lodged in those screens - it might help, but there's no way it will clean all of it out. Even soaking the thing and using a direct pressurized solvent spray doesn't clean them out. The carbon chunks are lodged in the screen. I have to scrape them out, or burn them out...with fire.

[nunya]

Did you have any work done to your crank or end up going with plus clearance bearings? I know 1.8t owners that went plus clearance bearings and others that had their crank polished, all of them ended up having oil pressure around 10-15psi, then to find out that they needed to run a thicker oil like 15w50 with those setups to get the oil pressure where it needed to be.

I will have to ask Christian. I didnt get a build sheet for the motor (dont get me started about the machinist they use). I will likely run a thicker oil just to make me sleep better at night. When at rev's the pressure is fine.

--dillon

[thenj3]

nunya, same thing happens with mine only have an issue at idle and its not all the time. I also have 034 coated bearings. Idk if anything was done to the crank during the build im thinking of just stepping up to a thicker oil. I'm picking my car up tomorrow so I'll be able to play with it after.

[Seerlah]

FWIW, I have low oil pressure at idle also. Light never comes on, and is fine when the car is actually driving. Even on cold starts, my oil pressure shoots over 100psi. Not sure if it is a gauge thing or what, because my oil pressure light never comes on and I know it works. Almost lost my engine before due to it, and my pick up tube being clogged to sh*t.

[walky_talky20]

Just an FYI for those not aware:

The B5's oil pressure warning system IS NOT ACTIVE at hot idle. Once the coolant temp is over 60C you could literally pull the drain plug and watch the motor seize up before you ever got a pressure warning. The oil pressure switch position is not considered for warning criteria until above 1500 rpm.

[Seerlah]

My warning light came on maybe 2-3 miles from my house after taking a long journey to Myrtle Beach and back (I live roughly 50 miles north of NYC). Engine had to be warm (), but I assume the light came on because RPM went above 1500 rpm?

[nunya]

Just an FYI for those not aware:

The B5's oil pressure warning system IS NOT ACTIVE at hot idle. Once the coolant temp is over 60C you could literally pull the drain plug and watch the motor seize up before you ever got a pressure warning. The oil pressure switch position is not considered for warning criteria until above 1500 rpm.

good info walky! keep me posted thenj3. I will likely have to do a similar thing.

--dillon

[syrinx32123]

Anyone know how to replace the oil switch. I think this is my problem. I can see that the wiring is starting to come apart.

[nunya]

Just to follow up, i gained about 4-6psi of pressure switching to 15w 50 motul. So hot idle is 12-14psi now.

[skim464]

still 12~14 psi is sickly low... how is ur 1.5k 2k 3k 4k pressure?

[nunya]

still 12~14 psi is sickly low... how is ur 1.5k 2k 3k 4k pressure?

Its like 60-70 cruising at around 80. Other people that use the machinist see the same pressure in 1.8T's. The machinist says its fine, so i guess i gotta take his word for it. It's not all just pressure, its also volume. I think the motors are built a bit lose. A certain company's time attack car uses this same guy as well.

--dillon

[thenj3]

I'm aassuming your running the 034 coated bearings? I''ve talked to others that have the. And their idle pressure is around 12 as well.

[nunya]

Yea, i assume since 034 built the motor. I try to not look at the receipts when i pay for things like this.

--dillon

[M-Hood]

I'm aassuming your running the 034 coated bearings? I''ve talked to others that have the. And their idle pressure is around 12 as well.

I have them and my idle pressure is near 20-22psi and that is on 5w30 redline oil.

[nunya]

I have them and my idle pressure is near 20-22psi and that is on 5w30 redline oil.

Did dan build your motor?

--dillon

[M-Hood]

Did dan build your motor?

--dillon

My motor was built back when 034 was at the small shop, not sure which machine shop did the work on my engine back then.

[Poopie]

i'm an RCH under 20 psi with my build 2.0l with a polished crack with standard bearings.

[nemick]

I think you should keep the state of your crack to yourself

[nynoah]

Let me be blunt. The weak point for this engine is the oil pickup tube. Its going to be WAY cheaper for you to drop the pan and clean it out than it is to buy another engine. Sea Foam - Auto RX any of that garbage is NOT going to clean out the hard gunk that is on that tube. Do it right, drop the pan and put in a NEW oil pickup tube. The more you drive it, the more damage you are doing. Buck up now or pay more later.