The brief
Charles brought his 320i in with an engine oil low warning, and a film building up around the top of the engine. He brought it in. An oil leak only spreads, the loss adds up, and a low engine risks low oil pressure and damage, so a low-oil warning isn't something to leave. On these engines the valve cover is a common source. It sits on top of the cylinder head and seals the top of the engine, and on BMW it's made of plastic. Over years of heat cycling the plastic warps and the integrated gasket hardens, so the seal lets go and oil seeps out the edge, runs down onto the exhaust manifold or other hot parts, and burns off, dropping the level. A warped plastic valve cover doesn't reseal, so it needs replacing.
The diagnosis
A check with the engine warm found it, oil weeping from the valve cover seal, running down onto hot parts. The rest of the engine's seals, the oil filter housing, the sump, checked out dry, so it was the valve cover. That's a replacement. The cover is plastic and warped and the gasket is built into it on these, you don't reseal it, so the call was a complete cover with a fresh gasket.
The work
The intake and the bits in the way came off, the old warped valve cover was removed, the mating face on the head cleaned up properly, and a new genuine BMW-spec valve cover fitted with its fresh gasket, every bolt torqued in sequence to spec so it seats evenly. The oil was topped to level and the engine run and checked warm for any weep. A road test confirmed the cover was dry, the level held, and the low-oil warning stayed off.
The outcome
No more oil weep around the engine, the valve cover sealed and dry, the level holding between checks, and the low-oil warning gone. The 320i went home with the leak sorted at its source. A warped plastic valve cover only seeps worse and keeps cooking oil onto hot parts, so changing the cover and the gasket stopped the leak and kept the engine where it should be on oil.
