help diagnose 202 squeak, water pump? - PeachParts Mercedes-Benz Forum

Ethan · #1 06-15-2007, 05:53 PM

I'm getting a squeaking scraping noise from one of the ancillary parts on the front of my 1998 (97K miles) C-230 (original owner). The noise seems to change with throttle and A/C operation. Get noise at a steady cruise on the highway and when at idle it seems to be more variable with it's loudness.

I was hoping someone could give me tips on how to determine if it is a water-pump, alternator, smog pump (have one?), or front crankshaft assembly.

Years ago my belt tensioner went bad, what I am getting now does not resemble that and the noise seems to emanate from closer to alternator or water pump.

I tried using a long screwdriver to detect vibration with no luck, I'll try a stethoscope.

Any advice on what a bad water pump bearing sounds like or an alternator bearing failure, would be helpful.

manny · #2 06-15-2007, 09:48 PM

Get a diagram of the belt-routing, remove the belt and spin every accessory by hand.
I would suspect the belt tensioner being defective ( again ), or the belt itself.
Only takes a few minutes to check.

Ethan · #3 06-16-2007, 06:57 AM

thanks Manny, It just didn't occur to me to remove the serpentine belt and spin all the accessories. Curious if I can detect the fault that way. Will give it a try.
I hope it is the belt tensioner, but my gut tells me it is the water-pump.

suginami · #4 06-16-2007, 10:25 AM

Also check the idler arm bearing. It is one of the pulleys that the serpentine belt loops around.

Ethan · #5 06-16-2007, 11:40 AM

I pulled off the serpentine belt and rotated all the pulleys (engine off) everything seemed O.K. as far as I could tell. Powersteering pulley made a mild clockwork type click every 180 degrees or so - but it seemed natural.

The alternator pulley seemd to have excessive axial play and lateral play - unfortunately I have nothing to compare it to.

Then I used a sethoscope with the serpentine belt installed and engine running and the clatter/chatter/squeal seem to be coming from the alternator and I saw a puff of smoke or dust wisp off around the alternator pulley.

I am going to search and find out if the pulley on the front of the alternator is a seperate replaceable item, I assume the alternator and alternator pulley for the serpentine belt is one unit.

Thanks Manny & Sugi for the advice, any and all advice is welcome.

Thanks.

david s poole · #6 06-16-2007, 12:17 PM

based on your tests it sounds like it's time for a new [rebuilt] alternator.the bearings have been known to make noise before the alternator quits charging.