Serpentine Belt squealing


New Member
Aug 9, 2011
Grants Pass
my serpenting belt is squealing and i can't make it stop. I have a 1987 mustang LX 4 cylinder NA 5 speed manual transmission. Since I started trying to fix the problem, I have replaced both the AC belt, the Serpentine belt, the water pump, the idler pulley, the alternator, I scrubbed all the debris off the pulleys, I even tried belt dressing, nothing makes this thing stop squealing! I went to NAPA and I was told the problem is that I bought my serpentine belt from someone else.
I am out of things to replace here, could the problem be the belt? It has the spring loaded tension pulley and it has plenty of spring in it, so I am confident that the tension is adequate. It sounds like the squealing is coming from the area near the water pump, but I am not positive. Could it be something related to the AC and I am just mistaken in thinking that the problem is related to the serpentine belt? The squealing happens even when the AC belt is taken off, so that makes me think it is not related to the AC. Anyone have any ideas?
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Delray Dude

New Member
Jul 7, 2010
I would suspect the bearing in the water pump is on it's way out. If you haven't replace the water pump in a while, you may think about doing it. you can replace it without too much difficulty.

I had a bearing squeal on mine - it turned out to be the bearing on the idler pulley - i squirted some PB blaster on it while it was running and the noise went away.

You could try squirting some at the water pump shaft while running and see if it goes away or reduces the noise - then it would point to the pump.


Apr 21, 2011
Just because the pump is new does not mean that it isn't causing the problem. Many new water pumps use junk Chinese bearings, and can be faulty out of the box.


15 Year Member
Sep 8, 2002
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After removing the belt, I would turn each accessory by hand and see if you can replicate any noise. Also, make sure your belt is the correct length and fitting tightly. Seems stupid, but stuff happens...

If there is no A/C belt, your compressor won't turn, so it can't be A/C Related. If you did not replace the power steering pump, it could also be in the power steering.


New Member
Aug 11, 2011
You may have over tightened your water pump bolts , and the back of the water pump is grinding on the metal behind it. good luck.