Obviously something is fubar w my pcv system.. why is my oil cap so hard to remove???

[2.7turbo]

There must be a valve that is bad - with the car running there is quite a bit of vacuum through my pcv system... the oil cap is very hard to remove - I know it's not normal as my 03 1.8t has even pressure under the oil cap when running... my 05 1.8t used to be the same but recently it's hesitating when on the throttle, turbo glowing red hot after moderate driving... I'm going to break something and I need to figure out which valve is fubar in the system..

Funny thing is the hose that goes from the pcv breather in the block up through a 3 way valve and into the side of the intake manifold is flowing lots of air... if i pinch it, the car acts fairly normal with minimal hesitation and the oil cap comes off easy just like my 03 1.8T...

What am i missing here - which valve goes bad? and how does the system flow air?? does it put the vented air into the turbo intake pipe or does it put the vented pcv air into the intake manifold??

any help greatly appreciated. i stfa and found ppl with the same situation but no fixes...

[2.7turbo]

really? no one has anything on this?

why is there so much vacuum in my pcv system?

[n7plus1]

pictures may help

[old guy]

This might help in understanding how it all works. The diagram is for a vdub but the A4 is essentially the same. It sounds like your PRV (pressure regulating valve) isn't functioning properly.

[gray6spd]

where does he find all these cool diagrams???? lol

[n7plus1]

OG do you think a malfunctioning "PRV" can cause a misfire?

[AudiBama]

Check all of your vacuum lines for leaks behind the intake mani


also check to see if your suction jet pump is flowing properly

[blackpool1974]

Check my reply below.

When the small valve at the bottom off that picture fails it will break the PRV with a couple of thousand miles, I have gone through 3 in 6 months dealer said he sells a couple a year. the picture on the post I made will be the offender

When both of these items go, you will get mega jerking at idle, loss of power and misfires and if you are really unlucky emissions light will flash intermittently


http://www.audizine.com/forum/showthread.php?t=311727

[2.7turbo]

blackpool; i took the system apart and clearly the pressure regulating valve is broken - question to you though... where is the pcv valve located? Does it go into a hose and therefore it's not visible? Does it go directly into the 90 degree pipe that come out of the block and then gets pushed into the 3 way valve that leads on one end to the intake manifold and on the other end up to the valve cover...?

[[email protected]]

This happened to me when my crankcase vent system went to shit. There was FULL vacuum on the engine and was basically impossible to remove the oil cap.

Check the hoses in your crankcase vent system, I'm betting the plastic one behind the motor finally gave into the oil soak.

That entire system is plastic and shitty. Here's a good resource: Click Click

I drew a beautiful diagram of the crankcase vent system

[[email protected]]

blackpool; i took the system apart and clearly the pressure regulating valve is broken - question to you though... where is the pcv valve located? Does it go into a hose and therefore it's not visible? Does it go directly into the 90 degree pipe that come out of the block and then gets pushed into the 3 way valve that leads on one end to the intake manifold and on the other end up to the valve cover...?

Your PCV valve is either located on top and to the rear of the valve cover...

OR....

Right on the TIP where the line goes up to the valve cover.

Either way, there's a line that goes from the valve cover to the TIP, the PCV is located on that line (either at the valve cover or TIP, depending on year). Big pancake valve, you can't miss it.

[2.7turbo]

Your PCV valve is either located on top and to the rear of the valve cover...

OR....

Right on the TIP where the line goes up to the valve cover.

Either way, there's a line that goes from the valve cover to the TIP, the PCV is located on that line (either at the valve cover or TIP, depending on year). Big pancake valve, you can't miss it.

thanks for the helpful info - if you look at the diagrams above, the pancake valve is actually the pressure regulating valve or PRV, the PCV is the positive crankcase ventilation valve which is the small 1.5 inch by 1/2 inch sized gray and black valve thats like $18... the PRV is $60 from the dealer. It controls flow from the TIP and regulates air from the crank vent system... The PCV valve controls air from the block to the intake manifold...

In my case the pcv valve and the prv were both shot... now temporarily i have my valve cover vent and my block vent just venting to atmosphere via tubes just dangling near the oil filter area. I have capped off the intake manifold nipple, and the breater going to the turbo intake hose. The car runs freaking great.. idle is perfect etc... now just waiting for my prv from the dealer ($60) and also to figure out where EXACTLY the pcv valve goes among those hoses...

Thanks for the amazing diagram above - really helped out quite i bit in understanding how the pcv system works...

[A4 Moda]

wow.

How genius is that?

Just like the Suction Jet Pump, this crankcase vent system was designed to provide the crankcase with vacuum ALL the TIME.

Good info

[old guy]

wow.

How genius is that?

Just like the Suction Jet Pump, this crankcase vent system was designed to provide the crankcase with vacuum ALL the TIME.

Good info

Yes it does. Here is something that I posted yesterday that I really though would stir up some controversy. Apparently no one saw it.

There is one function of the PRV / PCV combination that is often overlooked. During steady state cruising the PRV actually draws fresh air into the block and out through the manifold. When you pull off all that "stuff" the block can no longer actively expel bypass gasses entering the block from the combustion process (piston blow by, leaking valve guide seals etc). The block never gets 'ventilated' and can develop an internal sludge build up, especially if you do a lot of short distance driving. With a properly ventilated block the moisture gets purged out with the incoming air. Without the proper ventilation it takes much longer to dry out the moisture since the block is no longer actively being purged. After numerous short hot/cold cycles the condensation begins to build up and you can actually see it under the oil cap as a muddy looking foam.

Running an open line or a catch can will prevent pressure from building up in the block but the down side is that there is no active ventilation. There will be no "purge" air entering the block. there will only be a pressure relief from all the blow by gasses. This will eventually begin to create varnish like deposits from the high concentration of combustion byproducts remaining in the block.

[Papachristou]

so you are saying dont take out all that shit? diagnosticator says the same thing

[old guy]

so you are saying dont take out all that shit? diagnosticator says the same thing

Check my sig.

I can certainly understand how you can get frustrated with the whole breather system. Having a turbo definitely complicates things. However, if you take the time to fully understand how it functions it all makes sense. I have ~115K miles on mine and everything functions as it should. I have replaced several check valves and the suction jet pump but they were relatively cheap. I see no reason to pull it all out.

[Papachristou]

hmmm im fixing to put my BT on, i dont know if im going to keep that stuff or not. its not driven very much and i dont have a TIP to keep it all so ill probably end up junking it

i had wanted to keep my stock airbox and MAF but there doesnt seem to be a way without some custom stuff

[old guy]

Well obviously the car will run fine without it. Lots of guys are doing it. If you pull it all out my suggestion would be a more frequent oil change interval and consider adding a maintenance amount of Auto-Rx just to keep everything clean inside.

[2.7turbo]

all really great discussion i have enjoyed my 20 hours plus spent over the last couple weeks reading all about the pcv system etc...

Just a thought reading through all this... I'm thinking that to have the best of both worlds, which 1, is taking your vac lines out and having the car run flawless with no worries about vac leak here or there, if your pcv valve is functioning 100% etc... The other item of concern is properly venting your system... For me (and pardon my ignorance) the sludge build up / foam under your oil cap due to an improperly vented block is hearsay at this point... With the amount of blow by, (take your oil cap off when running and you'll see what i'm talking about) you'll notice the system blows out air at a decent clip... I disconnected my pcv system, plugged my intake manifold and plugged my turbo intake pipe. The amount of air being moved out of the oil filter pcv housing hole and out of the back of the valve cover vent is substantial.

In any case what i'm trying to suggest here is if you want to have your car run @ full power and also vent your block, then rig a small fan into the end of the custom hose you run to vent the block... similar to a fan on the back of a computer or laptop. This would pretty much have the same effect.

- love the help guys and 'old guy', you helped me quite a bit with the info in my 2 threads.

[rbj325]

Good info. I also feel the EVAP system is useful as well. I know that's part of "all that stuff".

[A4 Moda]

En Contraire, I read your posts and then it gets me thinking. Good info, as always OG>


Maybe you can help me with this question though.It's been bugging me. You know how one side of the crankcase vent goes to TIP, and the other goes to Oil filter housing, and then to a vacuum source where PCV pulls in fresh air?

Well, what's the purpose of the oil filter housing? Would it possible to bypass that system altogether?

Yes it does. Here is something that I posted yesterday that I really though would stir up some controversy. Apparently no one saw it.

[diagnosticator]

and how does the system flow air?? does it put the vented air into the turbo intake pipe or does it put the vented pcv air into the intake manifold??

It depends on if there is boost or not. When there is boost, the vapors flow into the TIP, if the intake is below ambient outside pressure, is a vacuum, then the vapors flow into the intake manifold.

[old guy]

all really great discussion i have enjoyed my 20 hours plus spent over the last couple weeks reading all about the pcv system etc...

The other item of concern is properly venting your system... For me (and pardon my ignorance) the sludge build up / foam under your oil cap due to an improperly vented block is hearsay at this point...

does this look like hearsay?



And that is with all hoses intact. Clicky click. Granted, it's a 3.0 but you get the idea about short trips and proper ventilation. Imagine if this motor was unventilated.

- love the help guys and 'old guy', you helped me quite a bit with the info in my 2 threads.

Glad I could contribute!

[[email protected]]

...consider adding a maintenance amount of Auto-Rx just to keep everything clean inside.

What do you mean by this old guy? Do a full flush with it, or just add a little to the oil?

Just wondering...

[old guy]

Maybe you can help me with this question though.It's been bugging me. You know how one side of the crankcase vent goes to TIP, and the other goes to Oil filter housing, and then to a vacuum source where PCV pulls in fresh air?

Well, what's the purpose of the oil filter housing? Would it possible to bypass that system altogether?

The connection above the oil filter is the block vent (or PCV valve). It is a one way valve that removes fumes from the block. When this valve is under vacuum the air is coming into the block from the TIP through the PRV (pressure regulating valve). It then flows through the block and out the PCV above the manifold and ultimately through the intake manifold to get burned off. If you remove that portion of the block ventilation system there will be no vacuum source to purge the block. You will still have a pressure release system through the PRV but there will be no clean air source to allow for incoming filtered air.

[diagnosticator]

En Contraire, I read your posts and then it gets me thinking. Good info, as always OG>


Maybe you can help me with this question though.It's been bugging me. You know how one side of the crankcase vent goes to TIP, and the other goes to Oil filter housing, and then to a vacuum source where PCV pulls in fresh air?

Well, what's the purpose of the oil filter housing? Would it possible to bypass that system altogether?

The oil filter base and crankcase ventilation oil aerosol seperator housing incorporated together cast into the block at that locaton is only a matter of convenience for design and manufacturing economy, there is no technical requirement the setup is arranged like that.

[diagnosticator]

Well obviously the car will run fine without it. Lots of guys are doing it. If you pull it all out my suggestion would be a more frequent oil change interval and consider adding a maintenance amount of Auto-Rx just to keep everything clean inside.

Yeah, as you noted, the presence of the turbo results in the complexity of the crankcase ventilation system. Together with the general lack of appreciation for the system as originally designed and configured to accommodate the turbo while providing effective crankcase ventilation under all driving conditions, removing the system has critically important consequences that are for the most part unknown to most guys who advocate this kind of misguided modification. Addressing the engines need for effective ventilation from some other arrangement is not likely practical and would be as complicated as the stock setup is. Ignoring the negative effects of removing the CVS on the engines overall performance and operational refinement is easy if the impacts of CVS removal are not known. Any tuner/engine builder having a full understanding of the systems involved would not advocate CVS removal IMO.

[diagnosticator]

all really great discussion i have enjoyed my 20 hours plus spent over the last couple weeks reading all about the pcv system etc...

Just a thought reading through all this... I'm thinking that to have the best of both worlds, which 1, is taking your vac lines out and having the car run flawless with no worries about vac leak here or there, if your pcv valve is functioning 100% etc... The other item of concern is properly venting your system... For me (and pardon my ignorance) the sludge build up / foam under your oil cap due to an improperly vented block is hearsay at this point... With the amount of blow by, (take your oil cap off when running and you'll see what i'm talking about) you'll notice the system blows out air at a decent clip... I disconnected my pcv system, plugged my intake manifold and plugged my turbo intake pipe. The amount of air being moved out of the oil filter pcv housing hole and out of the back of the valve cover vent is substantial.

In any case what i'm trying to suggest here is if you want to have your car run @ full power and also vent your block, then rig a small fan into the end of the custom hose you run to vent the block... similar to a fan on the back of a computer or laptop. This would pretty much have the same effect.

- love the help guys and 'old guy', you helped me quite a bit with the info in my 2 threads.

I believe that the CVS should be repaired if not functioning right, instead of ripping out the system wholesale fashion, and is easier than coping with the consequences of CVS removal all things considered.

[diagnosticator]

Good info. I also feel the EVAP system is useful as well. I know that's part of "all that stuff".

You are correct, I agree.
The main effect of removing the EVAP purge, is the loss of some fuel economy due to loosing the fuel vapors stored then burned in the engine during hot cruise, and increased air pollution. There is no benifit of removing the EVAP purge at all.

[rbj325]

You are correct, I agree.
The main effect of removing the EVAP purge, is the loss of some fuel economy due to loosing the fuel vapors stored then burned in the engine during hot cruise, and increased air pollution. There is no benifit of removing the EVAP purge at all.

Exactly what I thinking but wasn't sure about.