Oil in plug well

[Jared09]

Howsit guys , just a quick one so was doing a plug change yesterday and noticed the 4th plug was drenched in oil , it was very sluggy oil about 3/4 way up in the well , what could have caused this , and what is this knocking noise I'm getting on the intake manifold side , it's the N52B25 motor on a 2005 E90.

Thanks.
Jared

 

[Urban963]

AI Overview


The most likely cause of oil in a BMW B52 spark plug hole is a leaking valve cover gasket, specifically the inner gasket that seals the spark plug wells. Other possible causes include failing O-ring seals for the spark plug tubes, worn piston rings, damaged valve guides, or a cracked valve cover.
This video explains how oil can get into the spark plug wells due to a faulty valve cover gasket: