I hate oil seeping engines and one of the most chronic areas on a BMW engine is the valve cover.
Even after installing a new valve cover gasket, it's only a matter of days before it starts to seep, then runs down the rear of the head and trickles down the block just forward of the transmission bell housing.
I've solved the problem inexpensively.
Just a few finger dabs of 3M Super Silicone Sealant (clear) applied to the lower edge between the valve cover and head in the gap caused by the thickness of the gasket will do the trick.
Apply to a cool engine, preferably the night before. Clean off the surfaces with alcohol prior to applying the sealant. It won't take much and, if you're neat, it will hardly be noticed. When you're ready to adjust the valves, that little amount of sealant won't hinder you a bit in removing the cover. Just clean off the old and re-apply after replacing the cover.
Author: Stan Simm