Pully Noise? - PeachParts Mercedes-Benz Forum

mroliveira · #1 03-22-2007, 11:09 AM

Hi all,
I am brand new to this forum. I am looking forward to learn as much as I can from all the knowledge and expertise here.
I just bought a 1996 S420 with only 40,000 miles. I have only put on about 50 miles on it and have started to hear a noise coming from the front of the motor (center to left side) that sounds like a pulley.
Removed the belt and spun each of the pulleys (not including the fan), and there was no noise (probally because of no belt tension).
My question is: Can I remove each of the pulleys, grease them and put them back on, OR is by the time you hear a noise, TOO LATE?

Thanks in advance,
Marcio

TMAllison · #2 03-22-2007, 12:29 PM

Pull the belt on a cold engine and run it 30 seconds to determine if the sound is still present. If still present it's not a pulley.

G-Benz · #3 03-22-2007, 02:51 PM

If there is a small chunk of rubber missing on the grooved side of the belt, it will make a repetitive clicking noise over one of the pulleys.

It will sound more like a bad pulley than a worn belt.

Replacing the belt is a cheap and necessary repair anyway, and might eliminate the problem to boot.

mroliveira · #4 03-24-2007, 02:52 PM

This morning I took the belt off and started the car.
....the noise was gone!

So, I went out and bought a new belt and the idler pulley (not the one on the tensioner). The old idler pulley did seem a little loose.

I'm feeling pretty good, the new parts are in the car......so now I start it up......

The noise is still there!

I guess the next is the alternator. Would you replace it just because it's making noise? or would you wait till it goes out? How long can I get with a noisy alternator?
.....if the alternator was bad, wouldn't there be other sympoms????

Thanks again !!
Marcio

TMAllison · #5 03-24-2007, 05:36 PM

Now that you know the problem is an accessory device driven by the belt you need to spend more time testing pulleys to find the one with bad bearings or drag.

You already made two wrong assumptions. Thats an expensive way to find the problem as from here on the parts start getting costly.

Test them.

Spin them by hand, listen, feel and observe. You should be able to locate the offender.

mroliveira · #6 03-29-2007, 07:45 AM

I found the binding/noise!.....(1996 S420)
OK, I'm replacing the alternator this weekend. I bought a rebuilt Bosch 150 amp. for $230.00. (Mercedes price $880.00)
Is it best to get at the alternator from the top, or do I go from the bottom of the car?
Any Ideas on how much time it should take?
Thank, (again).