Noise under hood
 

On my 1990 300E I am hearing what sounds like a bearing noise near the alternator, belt tensioner or fan clutch area at rpms of around 1200-1500. Which componant would be the most likely culprit, or do you know of any other likely suspects?

Ohh no, is it sorta like a chirping noise? Well i had a chirping noise in my engine and it turned out that 87' 300E's had many problems with there blet tensioners and they usally had to be replaced once during the life of the car. Heh, i also thought it was a bearing, so did my dad until our mechanic told us the above info. Once you isolate the problem, call up mercedes if your a DIY and order it (it's a kit). I had mine installed it was a total of $500 but we got ripped off so id say like 350.

Good Luck, your car will run and sound like new once this is fixed.:D :D

Serpentine belts run around several pulleys, each with a bearing to carry the load. There isn't any particular bearing I know of that is the "usual offender". Isolating the noise is usually possible by listening with an automotive stethoscope (< $15 at most parts stores) or even a long screwdriver or combination wrench pressed to the component housing and just next to your ear.

You're listening for the noise that sounds out of place with the others. Most of the pulleys will make a smooth, whirring noise. A bearing on it's last legs will have a periodic scrape to it or just a continuous scratchy sound. Once you've identified the cause, you can estimate the repairs. Some are more expensive than others. I don't think a 1987 300E has the dreaded air pump just above the alternator (jump up and say "Thank you, Jesus!), so you're worst case is probably the water pump.

HTH,

someguyfromMaryland

heh oh yeah, if it really gets annoying i sprayed a little WD40 on the back of the pully and that dampens the noise, for a few miles that is.