mercedes vito, heavy knocking sound?

hi there. if its a heavy vibration on tickover, then i would suspect the flywheel. they have a 2 part (dual mass) flywheel, attached through a bearing/damper affair. if the bearing is failing, the centre section goes off centre, and causes the vibration.
ive never seen a flywheel actaully seperate, but it may begin to affect, and destry your clutch.
if its a whipping/droning noise, without vibration, maybe the belt tensioner is weak, or the alternator pulley clutch is siezed.

tony friel
December 2010