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Old 04-30-2002, 12:34 PM
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gsxr gsxr is offline
Join Date: Aug 2001
Location: USA
Posts: 8,102
Unhappy OM603 - oil leak from exhaust port with new head!

Hi all,

Check out the photo below. Yes, that oil leak is coming from the exhaust port, not the cylinder head. I cleaned the area with solvent & a rag, started the car, and watched the oil slowly appear at the base of the manifold/gasket area. A small air bubble would appear periodically as well. The quantity of the leak is enough that it drips all the way down the block and leaves a 1-2 inch spot under the car wherever I park.

Now, here's the bizarre part. I just put on a new cylinder head. This started after the new head went on. Oil consumption before the new head was about 1 quart per 7500 miles (basically nil). I've only driven ~500 miles with the new head but the oil level doesn't seem to have moved (i.e., still very low oil consumption). So I don't think the engine is conusming very much oil. The leak is more annoying due to the odor than the drip. The smell of burning diesel oil is quite pungent - much different than burning oil (on an exhaust manifold) from a gas engine!

Background info:

The old head had the rearmost stud broken off at the same port, and was leaking exhaust - there was a DRY carbon trail as proof. So, prior to the head job, there was no oil present there. From inspecting the old head, NO, the stud does not enter an oil passage, and the oil is not from a leak past the stud threads. The studs were pre-installed in the head from Mercedes. I used a Mercedes gasket kit from the dealer. I think it's possible (likely?) that the old leak warped the manifold, so it's not sealing quite right. However, before it was a "dry" leak, now it's wet.

What I don't get is how oil can be present at this point. If it were entering the intake, it would burn, right? I wouldn't get liquid oil, I'd get blue fumes. The valve seals are new, and the machine shop swapped over the old valves after checking them all out. Besides, with a turbo, there is little to no vacuum to pull oil past the seals.

There is oil in the intake crossover pipe and main charge pipe, more than I think is normal. It has to be coming from either the PCV (vent tube fro valve cover) or the turbo shaft oil seals. There's no other entry point upstream. I have the EGR valve disconnected. If the leak was due to oil coming through the intake, why wouldn't it appear at the other ports? OK, maybe because they're all sealed properly, and the oil is staying inside the manifold. But wouldn't I get a constant cloud of blue smoke out the tailpipe? And high oil consumption? Ditto if it was blowby. Compression is above minimim spec, btw, at 26-28 bar.

The turbo is the same as before the head job, and the blowby shouldn't have changed with the head job either. If either was the source I should have had liquid present at that port with the old head. The valve seals don't make sense either. I'm really stumped on this one. I won't have time to pull the exhaust manifold off for months to inspect further. I just wish I could figure out how this is happening. I'm going to pull the breather tube out of the intake elbow, and plumb it into a bottle or something, to eliminate that source. If oil is still present in the intake plumbing it would have to be from the turbo (KKK, no external leaks).

I get minimal smoke visible when driving or at idle. I did notice that when I rev the engine to ~3k when warm, there is noticeable (blue?) smoke. Also, once when I left a stoplight after 1-2 minutes of idling, the car left a cloud of blue smoke. But normally there isn't much there. And oil consumption (Delvac-1) is still extremely low.

I'd welcome any and all thoughts... there are more photos of the whole head replacement project at this URL:

Attached Thumbnails
OM603 - oil leak from exhaust port with new head!-oil_leak.jpg  
Boise, ID

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Last edited by gsxr; 05-01-2002 at 04:41 PM.
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