I have a 1999 E-300 (diesel) that has developed a belt vibration trouble. It has has a new belt, a new belt shock, a new (oldstyle) belt tensioner and a new belt pivot arm. The belt noise can be heard with the doors closed and the hood closed. Also can feel the vibration when sitting in the car. I ran the engine without the belt momentarily for diagnostic purposes and all the vibration and belt noise goes away. The motor mounts are good, the power steering pump and alternator move freely and do not appear as pulleys are out of balance. Does anyone know what could be causing this problem? I understand there is a "freewheeling pully" available for the Alternator and that it uses a different belt shock. Would this correct the problem? Any help is MOST appreciated!

Thank you!

 

Have you checked bearings (belt off) for play / roughness at each change of direction of the belt. i.e. water pump, alternator, tensioner etc?
Are the pulleys in line?
Is the belt following the correct path?

 

I did check roughness of belt in each direction change, even tried a different new belt. The bearings seem fine although I didn't pull them to check. I checked to see if possibly there was a belt part# change but there has not been. THe only thing I came accross was that there is now a free-wheeling pulley conversion for the alternator. It requires a different belt shock but I have not tried that yet. The pulley alignment looks perfect. AFter changing all the parts (first post) the vibration is better but still there. Was hoping someone has come accross this before. Thanks

 

OK, here is what it was. Mercedes does have a change in the Alternator pulley. It requires a special socket to remove and install but is a free wheeling pulley. After changing it all the noise and vibration is completely gone! Sounds like new again. THis also should keep the belt from beating stself and the surrounding parts silly like the shock and tensioner causing premature wear. So my problem is solved and if anyone else encounters the same problem (and you will know it) that is what it is!

Thanks,

Bob Stevenson