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  #1  
Old 06-15-2007, 05:53 PM
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help diagnose 202 squeak, water pump?

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.

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  #2  
Old 06-15-2007, 09:48 PM
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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.
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  #3  
Old 06-16-2007, 06:57 AM
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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.
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  #4  
Old 06-16-2007, 10:25 AM
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Also check the idler arm bearing. It is one of the pulleys that the serpentine belt loops around.
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  #5  
Old 06-16-2007, 11:40 AM
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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.
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  #6  
Old 06-16-2007, 12:17 PM
david s poole
 
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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.
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  #7  
Old 06-16-2007, 12:25 PM
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David thanks for the info, I'm searching for posts on the alternator pulley.

Is there ever a situation when the pulley on the front of the alternator is the only thing replaced?

Or is there ever a situation when a new alternator pulley should be installed on a new (rebuilt alternator?
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  #8  
Old 06-16-2007, 12:44 PM
david s poole
 
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it is rare for the pulley to be bad.unless it obviously has a chip out of it or is loose on the alternator shaft you can eliminate the pulley as a cause of your noise.
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David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg
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  #9  
Old 06-16-2007, 07:07 PM
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David, I thought about my last post about the pulley and realised I hadn't thought it out very well. I have a better understanding now.

Thanks everyone for the great help, really has helped me a great deal
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  #10  
Old 06-17-2007, 12:58 AM
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my alternator was done on my 97 at about 85k, 2 years ago, so it's surely plausible

May not apply to your case, but I've had cars including this one where I swore I heard metallic scraping noise, and it actually ended up being the rubber belt. Can fool ya sometimes.
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  #11  
Old 06-17-2007, 01:25 AM
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In the past when I have had a bad alternator bearing (on other cars) the screwdriver test has revealed a LOUD sound. If you have squeaking this could be the belt. One test is spray a little water on the moving belt with a plant sprayer (be safe, keep your self away from the belt!!). Spray it on one side then the other and see if the sound goes away for a short time. Old belts will squeak. I have already changed the belt on my C230 for that reason.

Mike
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1988 F150 144,000 miles (leaks all the colors of the rainbow)
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  #12  
Old 06-17-2007, 10:41 AM
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Will_w202, did you put in your replacement alternator yourself? if you did, I've been reading posts about using a prybar at a certain point of the procedure, if you know what I'm talking about could you elaborate.


Mike, my belt was taking a beating because the pulley on the alternator seems to be moving enough to cause some out of alignment rubbing. I tired to use a screwdriver but my car is a 4 cylinder with 97k mile engine mounts and I just couldn't be sure. (sethoscope seemed to reveal a bad alterntor bearing)

Also I do a lot of short trips in my car maybe seven or more trips of about one mile, so with not really understanding the facts I imagine my alternator and battery probably have a hard time.
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  #13  
Old 06-17-2007, 02:20 PM
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Well, if you do the alternator, definitely put a new belt on also!

Mike
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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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  #14  
Old 06-17-2007, 07:33 PM
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Ethan, it was done under warranty, so no.

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