VCG leaks from bolt grommets

[Slideways]

105k. Been pretty well cared for from when I got it at 45k onwards. All components of the PCCV system are relatively new (in the last 4 years/20k miles), including the oil separator, PCCV hose from the separator to the airbox (karb csl), and the airbox side airlines and ICV are all in good shape. Also I made sure to check that the oil return channel in the valve cover that is fed by the oil separator is clear. Anything I can look for to test the positive pressure theory?

Leak down test

If the leak is coming from the same two grommets, then there could be an issue with that valve cover or you have to throughly clean the mating surface. The studs are not removable without removing the cams. I would not worry about the guide tube seals. Mine does that on random cylinders and I just clean out the small amount that is there. I have no idea how it gets in there other than condensation. Spark plugs are completely dry.

[ATB88]

Leak down test

If the leak is coming from the same two grommets, then there could be an issue with that valve cover or you have to throughly clean the mating surface. The studs are not removable without removing the cams. I would not worry about the guide tube seals. Mine does that on random cylinders and I just clean out the small amount that is there. I have no idea how it gets in there other than condensation. Spark plugs are completely dry.

Had a leak down test about 3 years ago (at which time the same grommet leaking was occurring) and everything was as it should be. Of course, things could have changed between now and then but given that the grommets were leaking then and leaking now I would hope that this isn't the issue.

And actually, I think I can rule out mating surface of the valve cover: The outer/lower part of the grommet, where it contacts the valve cover mating surface is dry. The oil is seeping out in the center where the head of the stud meets the metal washer it sits on, suggesting that the oil is coming up through the center of the grommet, and that even the seal between the bottom of the washer and the top of the grommet is tight. But then why is the seal between the nut head and the top of the washer not tight enough?

As for the spark plug tube seal, I don't think it's condensation in my case. I can tell exactly where in the tube the oil is entering (just below where the upper part of the tube transitions to the lower which is part of the head), and if I leave it long enough (many thousands of miles) oil will pool at the bottom around the plug.

Thanks for all the suggestions so far!

[ATB88]

Here's a photo of the seepage so y'all can see what I'm talking about. Everything on the valve cover itself is totally dry.

[Slideways]

Can you swap that nut and washer to another stud?

[ATB88]

Can you swap that nut and washer to another stud?

Yeah I guess that's the move for now. I will say that before I refreshed with new hardware this particular position was always the first to start leaking, but it could be a coincidence, or if it's not it'll tell us something weird is going on there. I'll swap it and see how things look after I drive down south for thanksgiving!

[eacmen]

Are you sure there is no debris where the rubber grommet meets the valve cover? Might need to go at it with a pick and a scotchbrite pad.

[bmwfnatic]

Make some pictures with the valve cover removed, maybe we can spot something like your stud being too long.

[maupineda]

Add another washer. Maybe your cover is warped and the grommet does not seal well