cwilly3

I’ve jest replaced a broken serpentine belt. First I replaced a worn idler pulley on the right side. I have not replaced the tensioner. I installed the new belt following a diagram that I found for 2016 s550 coupe and everything looks and feels good. When I start the engine, I get smoke coming off the belt on the right/passenger side of the engine. Appears to be near alternator, but alternator pulley spins freely when belt is off. Nothing seems to be rubbing, belt squarely on every pulley, and belt is moving all components as it should. Tensioner is holding belt at firm tension but obviously something is wrong. Is the tensioner providing too much tension or is there another possible cause of the smoke? Any advice appreciated. Thanks!

Jud Chapin

First, I'd be sure I had the correct belt and one from MB.

okbarnett

All pullys spin and feel ok? especially the one you replaced?
Is it belt burning smoke? or electrical from alternator?
I replaced a belt at 35k and didnt touch anything else