Serpentine belt vibration - 1999 E300
 

I began to have a relatively loud vibration coming from the engine compartment, which I narrowed down to the serpentine belt and pulleys. I proceeded to remove the serpentine belt and noticed that it was old and had several very stiff spots it in - almost assuredly the original belt. I proceeded to jiggle the other pulleys and idler and did not notice anything feeling loose or worn out. However, now I have installed the new serpentine belt and the vibrations have not gone away, although the vibration does seem be be less. I also noticed that the belt does not vibrate all the time - likely coinciding with the AC compressor engagement. The car now has 123kMi. My question is - when replacing the serpentine belt on these cars, should I have just automatically also replaced the idler pulley, shock absorber, and/or spring tensioner?

I must say, it's a bit frustrating to go through the work involved in changing this belt and have the belt continue to vibrate - even to the smallest degree. Any assistance would be appreciated.

Thanks,

No need to replace the tensioner parts unless one is bad.

Try lifting the running engine 1/8" - 1/4" at the oil pan with a rubber bushing between the jack and engine and see if the vibration goes away. If so, it the motor mounts. You are not really lifting so much as taking some of the weight off the mounts.

Shock absorber is one source of vibration, it could be worn out or the bushes perished - makes a lot of noise when that happens.

If the belt is flapping around you have a pulley not doing it's job.

Take the belt off and rotate each pulley, also move them from side to side, check for excess play or grinding noises.

Belt tightener pulley is one to check:

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=210225&M=606%2E962&GA=722%2E608&CT=M&cat=19T&SID=20&SGR=045&SGN=03

Also check if the alternator clutch is functioning correctly.