Try:
http://forums.mbworld.org/forums/
Will answer any question you've ever had about an MB.
The ML's used to have a known issue with the harmonic balancer falling apart, I think they put it on recall. Mine grenaded on my E320 and a few months later they finally got around to fessing up and issuing a recall for the E320 engines too.
Afterall, just how do you maintain a harmonic balancer?