Rattle noise at startup.

[sweeper]

Hi Steveq,

Mines a C250CDi estate
Mine was noticed at 90K, it has full history but the service intervals seem way to long to me, between 15 and 18K miles.. but all done according to Merc recommendations, by Merc.
I got mine done at an indy merc specilist, engine didnt need to come out. The cut and fed the new chain on and fitted a new tension. All genuine mer parts.

I think it doesnt affect all cars with the om651.

I am now changing the oil every 6 months or 6K which ever is soonest for peace of mind. The chain can be done DIY but you need the right kit and patience. Not a quick diy job that.

Injectors out, cam cover off to acces the chain at the back of the engine.

Whats your cars, mileage etc??

It was more likely just the tensioner causing the rattle, the only issue in having it done with the engine in is that the guides can't be changed and these do sometimes break, leaving you with a constant rattle.
My Viano has 322000 miles, no internals have been replaced, only needing a water pump, alternator and a/c compressor according to the history, it rattles on start up, but so does my Vito which has done since new but it is more like diesel knock and goes after a few seconds and I put that down to advanced timing on start up.