[Stuart]

Any ideas why the throttle body on my 320d engine is collecting oil and then leaking? I say throttle body but I'm sure there is no throttle valve inside this bit but it was the nearest description I could find.

I've enclosed a picture of the engine with cover removed and the leaking joint circled. The black pipe is coming from the intercooler.

There are 2 possibilities:
1. The oil is being driven up from the intercooler along with the air (unlikely).
2. The oil is running down from the throttle body towards the intercooler.

Anyway a small puddle of oil collects at this joint and then leaks out. The seal inside the joint looks ok - maybe the pressure blows the oil past the seal.

My best guess is that the silver pipe up to the throttle body is the crankcase vent and oil is being blown up this pipe.

All ideas and opinions appreciated.

When I noticed the leak I cleaned it all up before realising I had removed the evidence. So now I'm waiting for the leak to look bad so as I can get it fixed on warranty. This gives me plenty of time to hit the forums ;-)

[Volume]

Originally Posted by Stuart

My best guess is that the silver pipe up to the throttle body is the crankcase vent and oil is being blown up this pipe.

I don't know much about turbos, but your last guess sounds very likely. Have you been driving at very high revs? That might cause oil to be sucked out the crankcase vent. From what I remember, BMW likes to use negative crankcase pressure for their engines, so it's quite likely that oil could be "sucked" into the intake.

Or you could already have wornout your cylinder rings...