Valve cover leak

[WingWheel7]

I’ve got a leak from right side valve cover. I’ve replaced the gasket with a new one. I believe previous owner replaced valve cover with aftermarket one since there isn’t a bmw part number on the inside. I’m out of ideas. Not sure what else to do.

[Mark S.]

What kind of gasket material?

[WingWheel7]

Gasket was bought from Max BMW. I assume it’s the factory gasket.

[Mark S.]

The reason I ask is because certain types of material tends to stick to the mating surfaces. Anything on the mating surfaces can prevent a seal.

[WingWheel7]

I cleaned both surfaces thoroughly

[ajaycad66]

Check for any "warpage" of the head cover. Aftermarket covers wont be up to OEM standards I would suggest, and could warp with the heating/cooling process.
Lay the cover on a piece of glass, (or a known flat surface) then use a feeler gauge to see if there is any difference between the glass and mating surface along its length.
This will hopefully indicate where the source of the leak is.