My service shop has me told horror stories about changing out the glow plugs on late model 300 d engines. Apparently they can break and fall into the cylinder head. I want to know if there are any super effective penetrating oils that will minimze this occurance or is this BS. I will reinstall the new ones using antisieze.

Thanks for meaningful help in the past.

Ted Sierocinski

I believe this is far more common in the later twin cam OM606 engines with the much longer glow plugs. I use a light coating antiseize on mine, but some counsel against that practice. You could also use a thread chaser and glow plug reamer to ensure against such eventualities, but I just don't think it's an issue with the OM603 engines.

FWIW it won't fall into the combustion chamber but into the prechamber.

When 606 glow plugs break apart during removal the part that doesn't come loose usually stays in the glow plug threads and has to be extracted like a broken bolt. I've never heard of a glow plug breaking apart during removal in a way that some part comes completely loose in the prechamber. The prechamber would have to be fouled beyond all functionality before there's enough crud to impair removal of the glow plug. Or am I an optimist?

Sixto
95 S420
87 300SDL