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I have a 2002 GMC Sierra 2500HD. The main belt constantly squeaks, it did not start squeaking until after I had my water pump and heater hoses replaced. The shop has replaced the belt 8 times over the last 2 months, and the squeak goes away for a little bit, then comes back. The shop mentioned that a pulley might be going bad, so I asked them to check it out. They said it wasn't a pulley and put another belt on it. It has started squeaking again. Does anyone have any idea as to what would be causing this?

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Can you describe the onset of the sound? Surely it doesn't start out as a constant squeal. – kahbou Mar 15 '12 at 19:09
It started right after the shop replaced my water pump, and heater hoses. With every new belt it goes away for 24 hrs at most, and then starts back up. It tends to go away after a few hours of the truck running and heating up. – BrettAdamsGA Mar 16 '12 at 14:27
I am chasing the same problem, seems like the water pump pully has slight wobble I have replaced every other pully the belt rides on so I'm going to changeout the water pump and we will see. I have gone through 4 belts last a month until start Sqweeking all the time. – user12510 Oct 4 '15 at 22:19
up vote 8 down vote accepted

Very carefully hold a large crayon,yellow works best, like a lumber yard might use against the edge of the belt while the motor is running.If the squeel stops you know its an alignment problem.The wax in the crayon will lubricate the belt and stop the noise.Try one side then the other.If you are lucky the yellow will be left on the misaligned pulley and show whether it is pushed in or out.

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That is a neat trick! – kahbou Mar 17 '12 at 10:48
Really cool trick, stopped squealing, I will be finding a mechanic tomorrow. Thanks – BrettAdamsGA Mar 19 '12 at 0:55

I would suggest a new shop. It takes a special kind of incompetence to try the same thing 8 times and expect different results.

A squeal can be caused by misaligned pulleys, although I've never experienced it. Here is a link describing this on an older Sierra where the power steering pulley is misaligned. Maybe the same deal is possible your water pump pulley.

Another thing to look at is the automatic belt tensioner. Read about it here. Replacing these seems common enough that multiple youtube videos were the first hits when I googled "gmc sierra belt tensioner". Go figure.

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I agree, have been talking to a few people about shops already. I have also thought about the tensioner pulley, but I have had other shops saying the pullies are fine – BrettAdamsGA Mar 19 '12 at 0:56

All very good answers to this question, but the recent work brings up another possibility. Many belts will start to squeal if they come into contact with even one drop of coolant. The cooling system should be pressure tested to see if any of the hoses or the water pump were improperly installed. A slow leak would explain the 24 hours before the squeal returns.

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I have had it pressure tested twice, did not find any leaks. – BrettAdamsGA Mar 19 '12 at 0:56

I think other posters have hit on your problem. You have a Pulley out of alignment.

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I'm not really sure how your answer adds anything to what has already been said. I'm not banging on you here, just letting you know SE doesn't function like a forum. We need constructive answers, not just agreement answers. This really should be a comment, especially since an answer has already been checked as the answer. – Pᴀᴜʟsᴛᴇʀ2 Oct 5 '15 at 23:20

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