Originally Posted by JamesM3M5
Need a new o-ring in the chargepipe. I pulled them out to measure and ordered ones that were a tiny bit fatter, but I can't remember what size. They are not available from BMW separately. I ordered a bag of them from McMaster-Carr.
It could also be oil from an oil filter housing leak making its way down there, but that usually cakes dirt on the front of the motor.
Anyway you could try and dig up the PN? When you say a little bit fatter, is that around 1/16" in cross sectional diameter or not even that much?