Seems like an amazingly simply issue but I can't find the detail I'm looking for...... My water pump seized at 80 mph on a very hot day going uphill. All the idler pulley wheels melted. I can't tell which ones had grooves and which were smooth to begin with - not to mention which ones go where...... Specifically, the tensioner pulley appears it may have had grooves, the other three forget it. There are two pulley guides below the oil filter that "sandwich" the belt and the other remaining idler sits above the alternator just to the left of the water pump. The two smaller ones measure 30mm wide and @ 54mm tall. The other two measure 28mm wide and one is 68.75mm the other is 70mm. No telling if the larger two used to be the same or not. Can anyone steer me in the right direction ?

Attached are the part numbers from the EPC for the pulleys you need. The EPC (Electronic Parts Catalog) is free for US residents. Instructions to join are posted in the Encyclopedia in the stickies on the opening page of the forum. You can also use this link to get started.

Hope this helps,

Bob

Thanks Bob !

I downloaded the EPC and it contained a missing piece of the puzzle. There used to be two different p/n's for the grooved pulley's and one of them was superseded to the same p/n as the other.

I wonder if that was when the belt length changed...

For the two idler pulleys in front that sandwich the belt you have an aftermarket replacement that's 100% better than the factory design . Go to speedriven.com or call them . Talk to marcin .... he's really nice and thorough on the phone . They are about 70 dollars each before shipping . I just ordered two myself for the family s600 . It's an 05 at 53k and the water pump pulley started wobbling and making noise . So I decided to change the water pump , pulleys and belt . Goodluck