Slight Oil Leak- Crankcase Vents & Oil Filler Neck

[LaszloT]

Confirmed that the crankcase vents at the top of my EJ205 cylinder heads (both sides) and the oil filler pipe neck have a slight leak on my new engine. Marked it 4. and 31. on the diagram below.

Likely gaskets weren't replaced during the rebuild, as they were also leaking here before.

Gaskets are not expensive and i can change them myself, without having to go under the car.

Some disassembly is required to get at them though.

http://i.imgur.com/VAr2SLN.png

It's wet down the valve covers and looks like it gets to the exhaust manifold on the passenger site.

With the right gaskets and filler neck O-ring, how long should I expect for this repair and are there any special considerations?

[LaszloT]

Vapor separators were weeping oil on the new engine, so I changed the gaskets.

Also got some mayonnaise in the vent system, which I didn't expect since I walk to work and only take long trips. Why might I be getting water vapor into the crankcase?

I was clear the gaskets were from the old engine so they needed to be changed, but I don't like the gunk in the vapor separator chamber.

Now I'm wondering if there's something wrong with the PCV valve? I don't expect weeping given this system is under vacuum most of the time - even if the gaskets were old. The PCV valve is recent - within the last year, or 30,000km.

[JoeT]

Forged pistons, right?

[LaszloT]

Yes, JoeT. 4032 alloy Mahle forged pistons, but had this same issue before it was rebuilt.

It looks to me like a non-functioning PCV system, even though the PCV valve was changed prior to the rebuild. There shouldn't be oil weeping from the crankcase if it's almost always in vacuum, according to my boost gauge.

[LaszloT]

Thanks to Epic and Keith for helping identify how the crankcase ventilation works.

The EJ205 has a center crankcase vent that is connected to the intake manifold and the intake duct through the PCV valve, as per the photo below.

The valve cover line that connects the vapor separators on each cylinder head is connected to only the intake duct, from the schematic diagram in EC(H4DOTC)-6 below.

Looks like air flows into the vapor separators from the intake duct at part throttle, and at WOT the flow is reversed to expel crankcase gases up out of the vapor separators as the blowby increases with engine rpm.

So the crankcase takes in cool air through the vapor separators from the intake duct at part throttle and expels hot crankcase gases through them into the intake duct at WOT.

Still doesn't explain why my vapor separators were leaking. I'd expect them to be under some vacuum at vacuum or boost. Is this correct?

Shouldn't the crankcase be under some sort of light vacuum in all operating conditions?

[JoeT]

That explanation is only partially correct.

A crank case should always be almost atmosphere neutral, that's the main purpose of the "Positive Crancase Vent", if there is a pressure differential in the crank case (positive), the intent is to expel that pressure and route it to either "Atmosphere" or to be more politically and environmentally correct, reroute it to the intake (vacuum side) where it can get recycled into the system.

The Vapor Separators should NEVER see any pressure or boost, because if you increase crankcase pressure through the Vapor Separator or blow by, "Overpressurization of the crank case" occurs which can result in thing like "oil burning" specially through the turbo slingers. Which results in nice blue smoke everytime it happens. Some of it is unavoidable as in Track Cars, but they too do their best to evacuate any pressure going to crank case.

So your head "vapour" separators are subject to the bernulli principal (you can read up on that) and the effect of fast moving air on pressure (vacuum), and never see any pressure.

The "Aeoli" or white stuff in your tubing is a result of water vapour mixing with oil, the most common "normal" cause of this is short trips. When you do a short trip, your engine never warms up enough to vaporize all the water in the system. Remember, the byproduct of combustion is..... (you can research this too, but the most prevalent byproduct is H20). Forged internals make this much much much worse too.. LOL Welcome to the Forged piston crowd. Overbuilding does not equal reliability, you can't even call it overbuilding, it's "Purpose building" does not equal reliability. LOL

They are leaking because either the Orings or the Fujibond has lived beyond their expected life span or your rubber tube's need to be refreshed. LOL

[LaszloT]

That's a good explanation JoeT.

I didn't realize that forged internals would worsen blow-by. I've changed the gaskets and O-rings I'll continue to address the age issues with the plumbing in my WRX, and that includes inspecting & replacing hoses as required.

[JoeT]

Remember waaaay back when we discussed your build, I actually recommended that you use stock pistons on your WRX for this very reason. Forged internals do not guarantee longevity, there is way more care and feeding to an engine with forged internals. Depending on the tolerances that you requested or chris requested on your build, it could take up to 20 minutes of running to get the oil up to a decent temperature and another 10 minutes of hard running (track work) to get the forged pistons to their "happy spot" of operations?

Now consider "winter", and cold weather. High silicone content pistons like the ones you have, still has tripple the amount of shrinkage per 100 degree C compared with the hypereutectic pistons that came with your car. Imagine the blow by? LOL

[LaszloT]

If this is normal for a built motor then I'm fine with it, and will consider it resolved. I don't mind tinkering with it and it's given me great service since it was rebuilt.

I'm just being an Engineer in trying to fix anything that's wrong with it. If there's nothing wrong with it then I'll just leave it alone and enjoy it.

Cheers, :)

[STeveD]

If you still feed PCV gases back to the intake, consider a catch can that you can easily drain.

[LaszloT]

As a wrap-up to this thread, I changed the vapor separator gaskets and the oil filler neck O-ring and the oil leaks went away. It's a miracle. :D

Why do I have to make some things more complicated than they are?

[JoeT]

They are leaking because either the Orings or the Fujibond has lived beyond their expected life span or your rubber tube's need to be refreshed. LOL

Glad you changed the gasket and O-rings... LOL

[LaszloT]

It takes a while for things to sink in with me, JoeT. But I did take your advice eventually. :)