Originally Posted by sixto

The M103 is not California friendly. You shouldn't have to clean the engine after replacing the valve stem seals. Go for a long freeway drive to burn off residual oil. You have a choice of holding up the valves with compressed air or filling the combustion chamber with string. Some caution to use a flywheel lock when using compressed air. There is a special tool that makes compressing the valve springs a snap but a heavy duty version of a VW water-cooled engine valve spring compressor should work. Work on one valve at a time, keep track of the valve springs, keepers and associated hardware, use only the latest MB label valve stem seals, and note that intake valve stem seals are different from exhaust valve stem seals.

How do you know you're not getting oil past the piston rings?

Sixto
87 300D