pully the one that wont move? if so that is why you shed the belt. the idler is one mounted on a pivot. it is there to take up slack as the belt stretches. these are a common problem on mb's.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.