dholt2775

Replacing the idler pulleys as part of routine maintenance on my 08 ML350. The grooved pulley and the belt tensioner both fit well. The existing smooth pulley does not have edges on either side of the smooth surface. The local MB dealer parts folks indicate that part (without edges) is no longer available; the current smooth pulley has an edge on either side. When I bolted the new part onto the engine, it would not turn. What I suspect is happening is that the edge closest to the engine is hitting one of four **** that are behind the pulley; that would prevent the pulley from turning freely. I asked the parts folks if there is spacer available that would hold the pulley out from the engine a few millimeters. They checked their records and there is no mention of a spacer. NAPA shows the same type of pulley that MB offers, so that is a no go.
The MB parts folks took a picture of the existing pulley (without edges) and said they'd check with MB USA for a possible solution. Has anyone here had a similar issue? Thanks!

MJ50

moved to W164 forum...

BlackML550

Have you checked the spares available at Rock Auto or FCP Euro? The pulleys have the lip you refer to, but the tensioner is smooth without the lip on the outer edges. Not to suggest an error in identifucation, but worth checking.

rapidoxidation

I've run into this on an aftermarket pulley. Had to take the pulley off the spindle and flip it over and it aligned perfectly. Problem solved.

dholt2775

Problem solved. Turns out the installed pulley was after market; we've owned this vehicle for four years and had not changed the pulley during that time. The MB version requires a different bolt, which I did not have. Once I had the right bolt, the MB supplied pulley worked like it should. Many thanks to those who replied.