1999 E300D

I've had a glow plug problem for a couple of weeks now....light stays on after startup. Also...of more concern...is a very loud knock on a cold start up. it goes away after a short while...and does not occur on a warm start up.

Can this be caused by a bad glow plug ....causing no combustion in that cylinder on cold start up.

It's a really loud knock....quite alarming...but goes away at higher rpms or about 15 seconds of engine running.

Can one bad glow plug cause damage if not fixed right away.??

Warren C.