Burning oil smell or smoke from the engine bay on an N55 BMW? Here's why the valve cover gasket leaks, what the repair involves and what owners paid.
If you own an N55 BMW long enough (335i, 435i, 535i, X3/X4 35i, M235i and friends), the valve cover gasket is going to come up. Usually the first sign is a burning oil smell at a stoplight, and owners swear it's coming from the car next to them. It isn't.
Why they leak
The valve cover on the N55 is plastic, and the gasket is rubber. Both spend years getting heat cycled right on top of a turbo engine. The rubber gets hard and stops sealing, and oil seeps out along the back and the exhaust side. From there it drips onto the exhaust manifold and that's your smell, plus a little wisp of smoke sometimes.
The cover itself is part of the problem too. On the N55 the crankcase vent setup is built into the cover. Covers can warp or crack, and when that happens a gasket alone won't fix it. That's why one of our reports says "+$600 if cover warped."
Symptoms
- Burning oil smell, worse after a drive or at idle
- Light smoke from the back of the engine bay
- Oil wet along the edge of the cover or pooling around the spark plug holes
- Misfires, if oil gets into the plug wells and the coils
What the job looks like
Cowl and covers off, coils and some wiring moved, the cover unbolted, cleaned surfaces, new gasket and spark plug tube seals, and back together. Bolts on these covers are aluminum on some cars and are meant to be replaced. It's not a nightmare job, but there's a lot of plastic clips and connectors that are old and brittle by now.
What makes one quote higher than another
- Gasket only vs new cover. This is the big swing. Our reports run from a few hundred dollars for a gasket to over a thousand once a new cover is in the mix.
- Coils and plugs. If they're due anyway, doing them now saves labor later.
- Region and shop rate. The highest report we have includes $1,000 in labor alone.
Before you approve it
Ask whether they checked the cover for warping or cracks, ask if the quote includes new bolts and plug tube seals, and ask what they'd do about the oil that's already cooked onto the exhaust. A good shop will clean it so the smell actually goes away.