An engine Oil leak may develop from the PCV vent housing on the valve cover and/or the inspection plate on the front of the engine.Google+
Car Problem Reports
Mercedes-Benz E320 4MATIC Oil May Leak From PCV Vent Housings and Inspection Plates
Mercedes-Benz E320 4MATIC Problem
Visitor, 2003 Mercedes-Benz E320 4MATIC, 44,000 mi
MB Mechanic said the same thing to me. But I don't know the impact this will have if not treated.
Visitor, 2004 Mercedes-Benz E320 4MATIC
I have an wagon! I thought the head gasket was going but realized that couldn't be the case. It has to be the PCV housing. It's not much. I lose about a quart every 15,000 miles. But it's annoying. Sometimes it the oil drips on the hot engine and smells like it's burning oil.
Visitor, 2001 Mercedes-Benz E320 4MATIC
noticed oil leak all over valve cover and coils. in process of taking apart looking for leak or leaks