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Opeler
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Discussion Starter · #1 ·
My '70 GT has developed a whine above 4000 rpm. I have a feeling it is the alternator belt, but if it was slipping, I would have expected some fluctuation to be recorded on the ammeter, which does not seem to move when the noise starts. Could it be another belt. or something else altogether? The noise is very high pitched, almost a screeching.

I should note that I recently had the alternator off to replace the mount bushings. At a glance, the belt didn't look too bad, and since I didn't have another one handy, I put it back. I think the tensioner is as far as it will go, but I might be able to get another mm or two movement out of it.

What is the recommended belt size for this application, and does anyone think I should check anything else?

Thanks,
Andrew
 

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70's Opeler, back 4 more!
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398 Posts
There's only one belt on my 1.9 engine and it drives the waterpump and the alternator.

You might look at the belt you are running and compare it to the spare you have, looking for stretch, excessive wear, or, like Old Hippe stated, glazing. You might even try installing your spare to see if that clears up your problem.
 

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Another possibilty might be wheel bearings that are starting to go. They often will whine only at certain rpm's when first wearing out before sounding off on a continual basis. I had a 74 VW Dasher wagon that started out the same way and turned out to be wheel bearings.
 

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My guess is a bearing, either a water pump (which sounds like what you are describing) or an alternator bearing. Try isolating it by using a stethoscope (a child's set from a local toy store will do, or steal it from a child. Or a doctor) to see where the noise is emanating from.
 

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Opeler
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Discussion Starter · #6 ·
Thanks for the suggestions everyone. I actuallyhave a mechanic's stethoscope, but how can I get in there to listen to the water pump with the engine at 4000+ rpm? It seems like I run a pretty good chance of cutting an arm off.
 

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I recently had a similar situation. My whine started soon after installing the Chevy alt. It would begin at 3500 rpm, but didn't really sound like the belt, which was tight. I tighened it some more, and it quit. I now have it tighter then I like, but it's quite.
Might be worth a try.
Jc
 
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