BMW M54 6-Cylinder Oil Smoke – Smell, 3-Series, 5-Series, X3, X5, Z3, Z4
This answer is applicable for many BMWs in addition to the one listed below.
car year: 2005
car model: 330Ci Convertible
About a year ago I began smelling oil and seeing faint smoke from the driver side of my engine compartment (back corner near the driver). It was not every time I drove the car and seemed to be more prevalent on long trips or when I pushed the RPM’s on occasion. After numerous trips to my mechanic who could find no oil leaks or other symptoms he finally replaced the Valve Cover Gaskets and the problem seemed to go away. That is until a few weeks ago…symptoms are back and while not as frequent as they were a year ago they are definitely the same – oil smell and faint smoke from same area of engine compartment and definitely worse when the car is “pushed” for a short sprint. Could this be a PCV issue?
The most likely case is that you may have another leaking valve cover gasket. If you have a partially clogged PCV oil separator check valve assembly (commonly called OSV or CCV) or oil drain line (from the valve through the dipstick tube), this can build pressure in the engine crankcase and can (and does) cause various gasket leaks. The most common being the valve cover. The increased symptoms when “pushing” the engine could be due to more oil being inside the valve cover at higher engine speeds as well as the higher heat generated by both the engine and the exhaust.
Certainly, there could be another leakage point, but if it does not appear that the oil pan, rear crankshaft seal, timing cover or oil filter housing gasket (on the driver’s side of the engine, and very common) are leaking, we would consider the valve cover as the likely culprit. In this case, the recurrence after a gasket change would be due to poor replacement work or a partially clogged PCV (crankcase ventilation) assembly.
For fluid leaks that are difficult to diagnose, we do offer a DIY leak detection kit. This is a smaller version of what a professional shop would use to locate the source of a leak when regular visual inspection is difficult or impractical. The kit includes various fluid dyes (for oils, coolants and A/C systems) that are added to the fluid (engine oil, for example). The system is operated long enough for the leakage to start including the dyed fluid. A UV light (included in the kit) is then used to view the leakage area. Under the UV light, the dye will glow and this can be traced to the origin of the leak.