Intermittent burning oil smell in 2001 BMW 525i

I have a 2001 BMW 525i with 121k miles. For the past 18 months I occasionally get a strong burning oil or rubber smell only after I brake. When it first started the check engine light came on and all the sensors and codes were checked. The smell comes from the AC vent. It happens maybe once a week and then can go for a month or so without happening. I have had good mechanics check the exhaust system, brakes, change the valve cover gaskets, chance an internal PVC pipe of some kind and I am stumped.

If it happens only when you brake, here’s what I’d try. Drive until the engine is fully hot and then park on the steepest downhill you can find with the engine idling. Pop the hood and watch for ten minutes or so for any wisps of smoke. If you don’t see anything, try angling the car across the slope in each direction.

Even though the valve cover gaskets have been checked, I still think they’re a likely culprit here.

Thanks so much for the suggestion. In retrospect it might to be related to sitting on the slope of an Interstate off ramp. I will check it out.
Best wishes,

Check the oil pressure sending unit for leaks, it’s easy to miss.

Ed B.