Abrasive noise on cold starts in 1999 Mustang GT - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 06-04-2010 Thread Starter
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Abrasive noise on cold starts in 1999 Mustang GT

Hi everyone-

My 99GT (totally stock) recently started making a constant noise on cold starts that I am having trouble diagnosing. It sounds basically like a motor or fan bearing going bad because it is a fairly loud whir resembling parts rubbing (there is no screeching), but the particular tone makes it hard to determine where it is coming from. It modulates just a little when the a'c compressor kicks in and out, but it is still audible when the a/c is off.

So far (about 3 days), it goes away after a few minutes of the car running and it is worse when I start it in the morning that in the afternoon when I leave work. I notice no ill effects in performance, but I don't want to wait for that to change, ha.

Any thoughts on what parts could be causing this? Alternator, belt, or even something physically rubbing up against a moving part? About to take another visual inspection, but I thought I would see if anyone else had experienced something like this.

Thanks!

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post #2 of 6 (permalink) Old 06-05-2010
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Could be any one of the rotating components in there. You can take the belt off and run the motor to see if the noise dissapears, thus ruling out the motor. Chances are it's an idler or tensioner pulley. Use an automotive stethescope, long screwdriver or some other reasonable facsimile and listen to each piece. You'll be able to pin it down this way.


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post #3 of 6 (permalink) Old 06-09-2010 Thread Starter
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Turns out it was the belt tensioner pulley and one of the idle pulleys that was making all the racket. Bearings were just getting tired after 125k miles I guess. Replaced them both and it is back to normal!

Thx
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post #4 of 6 (permalink) Old 06-09-2010
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Quote:
Originally Posted by gfunkusarelius View Post
Turns out it was the belt tensioner pulley and one of the idle pulleys that was making all the racket. Bearings were just getting tired after 125k miles I guess. Replaced them both and it is back to normal!

Thx
yeah I did that not too long ago too, however I had my main serpentine belt break, so it's good that you caught it beforehand. FYI, the radiator fan motor can go at anytime too, so be aware of that....
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post #5 of 6 (permalink) Old 06-10-2010 Thread Starter
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Thanks for the heads up. The fan was the first thing I spun up as I was concerned it might be the issue, but it sounds good for now.
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post #6 of 6 (permalink) Old 07-01-2010 Thread Starter
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Just as a follow up to this-
When I had those pulleys replaced, they were a bit concerned the A/C Compressor might be going bad and might have been the source of some of the noise, but they were never able to recreate the bad sound I had heard. Ends up their concerns were valid. A few days after changing the pulleys, the noise came back and I let it continue since it was hard for anyone to find the noise since it went away after a few minutes.

Eventually, it was audible all the time and then I started hearing a definite metallic clanking, so when I looked again, I could see that the metal plate on the face of the compressor had broken free, so when the compressor was running, it was jamming tight and when it wasn't, it was flopping around. SO the noise was still some sort of internal bearings PLUS this metal plate. It was starting to wear thru the metal, too, so it was very obvious and I got it replaced.

I guess replacing the A/C Compressor after 11 years and 125k miles isn't too bad, but the thing was still blowing cold air!
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