PeachParts Mercedes-Benz Forum - View Single Post

MB-Dude · #2 08-02-2007, 11:53 PM

I could be wrong, but I think what you are describing is the crankcase ventilation tube - the one that goes from the valve cover to the bottom of the air cleaner. Its purpose is to draw crankcase fumes into the air intake, so that they get burned through combustion, as opposed to simply being released to the atmosphere.

Since the idea is for intake vacuum to draw the fumes into the intake, oil vapor also gets drawn up the tube. This vapor can condense within the tube, but should drip back into the crankcase, if properly installed. Hence, the oil you found inside the tube. It is not uncommon for some oil to be found in the tube, but if you have a noticeable amount (say, teaspoons full), and then you may have something causing your crankcase pressure to rise abnormally - rings, etc.

If you smell oil fumes in the cabin and outside the car, you either have an oil leak or your crankcase ventilation system is not properly connected. Also, perhaps you dripped a little oil on the exhaust manifold yesterday.