I had my valve cover gaskets replaced three or four months ago which cured this problem for a while but it is now back with a vengance! Hard acceleration and high rpm driving in general produces a strong oil smell in the cabin. I replaced the oil filler cap with an M3 piece which seems to have cured that leak. I looked in the plenum today, very clean. What other parts could be leaking oil or causing this stench?
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I swapped out two of the oil separator hoses and cleaned up the plenum (though there was not much in there at all) today but it still smells. I think I will clean more of the engine and see if that helps. Will oil that may have been spilled on the engine eventually burn off or will it remain there and smell every time it is heated up? Is it safe to use throttle body cleaner to get rid of oil spilled on the engine? I know it is flamable but does it evaporate off after a few mins?
Does it smell in the cabin? Or is it when you park and stop you smell it?
Sometimes after a long spirited drive if I get out I smell the exhausts I can smell a faint oil smell. I think these high-compression engines just do that. If you smell it when driving it may just need new cabin filters or to ensure they are securely connected. If there is oil that has dropped somewhere, it will burn and smell almost immediately, I doubt it will stay there and linger and burn and smell again every time you drive the car. Perhaps you have a minor oil leak dropping oil onto the exhausts, like others said I would drive the car and then check for leaks. What I would do is clean the engine thoroughly, then when you stop after some spirited driving, run a dry white towel around the block to check where the oil may be leaking from. By no means is this a very... professional way to test, but it is definitely a cheap and effective way to test for leaks and where the source of leaks may be.
Is it possible your VCG's were replaced with cheaper units that are not up to par and have started leaking again?
Have you checked in front and below of the VANOS units? I had worn O-rings which resulted in oil slowly dripping out and onto various parts in the engine bay area. ie: hoses etc. The oil smell was evident, but the removal of the under-tray allowed me to pin-point the area in question and onto this board I went searching, and sure enough other members have had it happen to them also.
Are you certain it's leaking oil and not just oil burning in the combustion process? I'm just wondering if it's not just a completely normal side effect of hard acceleration. Most cars smell a bit of oil if you give them a good spanking, and my M5 more than any other I've had.
On the other hand, I've spilled oil when filling up, which has then dripped down the side of the engine, and you get a much more acrid smell coming into the cabin as it burns on the exhaust header. You also get a cabin full of seriosuly nasty smoke if you spill enough! (oops!)
Is it possible it's just normal?