Crankcase Pressure - reducing it

[JAG]

My VW GTI 1.8L Turbo has a hairline crack in the top of the dipstick. What this has shown to me is that enough crankcase pressure builds up to force a little oil through the crack. Some modified versions of this engine have even blown their dipsticks out of the tube during high boost...at least I don't have that going on.

It would be good to lessen that pressure by evacuating it by a route in addition to the usual PCV system, which clearly isn't "keeping up" with the pressure buildup. That pressure is from chemically nasty gas/solids which degrades the oil.

So a thought occurred to me. Take out the dipstick and replace it with a hose with a one-way check valve that leads to a catch can and finished off with a high efficiency miniature air filter. This would possibly allow pressure to escape while the check valve prevents sucking outside air in during crankcase vacuum and the air filter would filter outside air that does squirm past the valve when closed. The catch can would condense some of the oil/water mist so I don't turn my engine bay into a stinky oily mess.

It may require some overall design tweaking to work well. I know this is NOT needed. I just think it would be a neat project. Have any of you heard of any similar setups?

 

[wavinwayne]

It's no stranger than what some of the guys do on the vwvortex. I say go for it, and post pics and instructions.

 

[SZR48207]

How about adding a breather to the valve cover?

 

[Shannow]

A breather would allow air in, which JAG has said that he doesn't want to do...

the proposed system sounds doable and workable.

Could put in a full blown pan evac system too.

 

[Ben99GT]

Take an electric smog/air pump from a BMW or Ford, plumb in into the PCV routing, use a check valve between the PVC valve and pump line to retain use of the PCV, and use an RPM activated window switch to activate the air pump at high rpms. That will allow you to pull a few inches of crankcase vacuum at higher rpms.

 

[OVERKILL]

Crankcase evac pump maybe? They are normally a race item but......

 

[The_Jeff]

I like it. You could also just put in an on-off solenoid, inline filter and old-fashioned road draft tube, the venturi effect would help scavenging. The oily mess wouldn't be on top of your engine, maybe somewhere underneath or gone entirely!

 

[Steve S]

Would modifying the pcv cause the engine to run bad?

 

[mechtech2]

German cars have used odd PCV systems, and not just on turbos.
I would fix the crack . Even tape it, at a minimum!
Go online to specifically seek out upgrades to your car - look in dedicated forums. See what the guys there say and do.
And think three times before modifying it!

 

[JTK]

Is the cracked dipstick tube easily replaceable? If not, how about just slide a section of hose over the cracked dipstick tube, hose clamp it at both ends and call it day? I wouldn't 'vent' excess CC pressure through a low point like a dipstick tube. That's just asking for problems. I have heard of turbo'd and SC'd gas engines having this problem. If anything, I'd route an additional hose from cam cover to clean air tube.

 

[JAG]

Thanks all!

The ideas have been helpful. I'm not going to add anything electronic though.

The dipstick has a plastic top/handle. That is what's cracked. The dipstick tube is also plastic. The tube is at a high point: around the height of the cam cover, so there are not worries about height problems.

There already is a hose coming off of the cam cover.

Getting the hodge-podge parts that I need to fit together will be the hard part.

 

[SHOZ]

I have a catch can, really a condensation can, located inline with my PVC system. It has a spring loaded check valve that is pulled closed when under engine vacuum. I seal off the crankcase inlets and run ~10" Hg on the crankcase.

I don't know how much the check valve could pass when the crankcase is pressurized. It does and excellent job of dumping the snotty gunk when the car is shut off though.