Crankcase pressure?

[Dsm_Roly]

Okay so I turned on my car after a long time of working on it (tranny swap, Big 16G, suspension touch ups). It starts fine but it seems the it's venting alot of smoke from the valve cover. It's getting out through the pcv valve and the nipple on the left side (when unvented). I can take my oil cap off even a little and it still seems like a high pressure kind of smoke? Any idea's? I'm starting school next week and need to get this puppy up and running!

 

[91-gsx]

The PCV valve is at the top left of the valve cover, and has a hose that leads to the intake manifold to create vacuum and draw those fumes into the intake manifold. The nipple on the left side of the valve cover should have a hose running to it from the intake system, between the turbo and the MAF sensor. If these systems are hooked up like outlined above(Or should I say stock) you will not get any visible smoke/fumes/blow-by. If you don't have the system hooked up this way, or have a very extravagant PCV evacuation setup, (Which is not worth it at this point in your modification list) then you will end up with way too much crankcase pressure... I would go with the stock PCV setup. When I tried to vent them for a while with the stock PCV and the nipple on the left side of the valve cover running to a catch-can, the car ended up having a lot of smoke come out of the exhaust because there was to much crankcase pressure... I then found out that hooking up the stock PCV system back would not stop the smoking because the excess crankcase pressure messed up my valve seals in that short period of time... Once I replaced my valve seals, I never modded the stock PCV setup again, it works too well. Later.

 

[91 TSi GP]

Hmm ok my car has alot of pressure coming out of the nipple on the CAS side of the valve cover. My car just has one of them ### breather filters on there. So if i route a hose from there to my IC piping before my MAF it will help out alot?

 

[91-gsx]

Hmm ok my car has alot of pressure coming out of the nipple on the CAS side of the valve cover. My car just has one of them ### breather filters on there. So if i route a hose from there to my IC piping before my MAF it will help out alot?

So you have a breather filter on the nipple, on the left side of the valve cover? What about the top nipple, which is really the PCV valve.. What have you done to that one, or how do you have it routed? It should have a tube going from it, to the intake manifold, does it? Are you the original poster with another name, or is this another person?

 

[91 TSi GP]

So you have a breather filter on the nipple, on the left side of the valve cover? What about the top nipple, which is really the PCV valve.. What have you done to that one, or how do you have it routed? It should have a tube going from it, to the intake manifold, does it? Are you the original poster with another name, or is this another person?

another person. Yeah i got the breather on the left side nipple and the pcv valve has the hose running to the intake mani like it should..

Basically what i was getting at is I should run a hose from where I have the breather filter back into the IC pipe?

 

[91 TSi GP]

so this is what it should look like technically. The red squiggles are the hoses

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[91-gsx]

so this is what it should look like technically. The red squiggles are the hoses

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I see what your saying... So you have a GM MAS I'm assuming... You have the top part with the PCV valve hooked up right in the picture. But you want to run a hose from the nipple on the left side of the valve cover to the inlet of the turbo, when I said you should run the hose in between the MAF sensor and the turbo, I thought you had a stock 1g/2g MAF sensor.. So the hose on the left side of the valve cover should be routed to the intake system that you have on the turbo, unless you running the turbo with no intake pipe or filter? Here is new play on your picture to show you what I mean:

 

[91 TSi GP]

Yeah i have a gm maf. Thanks for clearing that up for me! ill be sure to re-route that this weekend

 

[kenamond]

Okay so I turned on my car after a long time of working on it (tranny swap, Big 16G, suspension touch ups). It starts fine but it seems the it's venting alot of smoke from the valve cover. It's getting out through the pcv valve and the nipple on the left side (when unvented). I can take my oil cap off even a little and it still seems like a high pressure kind of smoke? Any idea's? I'm starting school next week and need to get this puppy up and running!

Since someone hijacked your thread...

It sounds to me like you have a lot of blowby for some reason. Have you checked compression?

And have you done something non-stock to your PCV system?

 

[rstchris]

You should clean out the PCV valve if you have not done so, it may be gummed up and not able to suck.

 

[Dsm_Roly]

Ya I figured out my problem. My rings a seals were shot I'm in th middle of a rebuild right now

 

[Rob10_99]

For some reason people always, always, always route the blowby back into the intake tract, this causes nothing but problems with turbo cars.
The gasses that come from your crankcase are hot, steam, and oil(among other chemicals).
Your coating your entire intake system with oil and buildup, if you run a blow through I suggest you just vent it. Even after your rebuild just hose to a catch can.

 

[BeatupVR4]

Since I've never seen anyone explain correctly the way the system is designed I will give it a shot.

When under a vacuum condition (idle, cruising) the blow-by gasses are going to want to be sucked out of the valve cover via the PCV valve vent and down that short hose and into the intake manifold.

When you switch over into a boosted condition the PCV valve "theoretically" closes. I say this because if you blow on it in the reverse direction it will attempt to seal up but leaks even under the 1 psi you create while blowing, hence the need for positive check valve kits. Well when it "closes" the gases will want to be sucked out of the other port because in a stock intake setup (and even lots of modified setups) while pumping enough air to make boost the intake tube will be under vacuum caused by the MAF/air filter assembly being a restriction to the turbo.

So it's basically just switching sources from where it gets it's vacuum. Ever notice NA cars don't have that other port besides the PCV valve? Because they don't need to worry about a boosted condition.

As another post stated when routed into the intake pipe you get LOTS of oil buildup in the intercooler and such. But these gasses are also dirty and corrosive and you don't want them mixing with your oil (hence the reason for the system in the first place, well that and piston rings are much happier in a low to negative pressure crankcase) I like to trash the PCV and get a check valve but keep it routed into the manifold and either just run a hose from the other port to the ground or get a properly set up catch can system.

EDIT: After looking at that silly drawing again, in a blow through setup you REALLY don't want the line going back to the intake pipe. All that crud air will mess up the filament right quick.

Also to the OP I was going to suggest checking the rings but you already figured that out.

 

[DirtyBirdRacing]

so this is what it should look like technically. The red squiggles are the hoses

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This drawing isn't correct. The hose from the fitting on the left hand side of the valve cover must go on the compressor inlet pipe before the turbo.

This way the crankcase pressure is relieved while the engine is under boost.

When you run a catch can you need to replace the PCV valve with a hose barb or some other fitting that is not a one way check valve.

As far as the hose connecting the valve cover to the compressor inlet pipe. You can hook this line up to the compressor intake pipe with a small inline filter in it to get rid of the oil and residue that is in the crankcase blow by. Or you can take this line, put an inline filter in it and route it out the bottom of the engine bay with a cap on the compressor inlet pipe where this hose would go.

Bill