Noisy Serpentine Belt


New Member
Mar 6, 2010
My Mustang's belt has started to squeal (again.) Based on many suggested tests, we have determined that it is not a tension or pulley/bearing issue. The noise is definitely from the belt. (The car had front end damage before it came to me. I found out that my dad, who picked up the car for me, replaced the tensioner and the belt. The car had 30,000 miles on it at the time and now it only has 33,000.) The tensioner does not bounce around and loading the system and increasing the tension on the tensioner do not make a change. They pulleys themselves are also without noise.

Yesterday my husband placed one drop of water on the smooth side of the belt and the sound went away instantly (different squeek sound) Today that did not work.(Very wet day today and the squeel is LOUD) He then placed one drop of water on the ribbed side of the belt and the sound again went away. (We made a video, but the sound isn't clear enough for you to hear - so posting it wouldn't clear anything up.) He then varied where he placed the drop of water - back rib, center rib and front rib - it doesn't matter where the drop is - the sound goes away for 30 seconds to 1 1/2 minutes. You can see the moisture evaporating off the belt and the squeeking starts as soon as it dries off.

Adding load to the alt. and air cond doesn't change the noise.

ALL the pulleys spin freely with no slop in the bearings. The belt ribs are dull black and show NO sign of glazing.

So, now that I have freshly and thoroughly scrubbed pulleys and a new belt that squeaks - any squeaky belt cures? (If not, I'm going to run a tube from my wiper cowl to the belt and set up a drip system!) :shrug:
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New Member
Mar 5, 2010
wow, sounds like a PITA. other than chasing the exact pulley thats squealing. have you tried a yardstick or similar(straight edge) to check alignment of pulleys. like laying flush on crank pulley and rotate like clock hand and see if any others are bent or not in line?


New Member
Mar 17, 2010
In my experience there are ONLY two causes of this reoccurring noise. Pulley misalignment, or anti-freeze getting on the belt. Pulley misalignment being the most likely cause. I have had cars come through the shop with this issue, and have found that another shop had replaced the power steering pump, and when the pulley was pressed back on the pump shaft, it had either been pressed on too far, or not far enough...and we are talking mere millimeters, not something you'd see by looking at it from the top or sides by eye. There is actually a laser alignment tool that will allow an alignment check...made by Gates belt if I remember correctly. You may search out a shop that has one.

I have also accidentally spilled anti-freeze on the belt before and caused the SAME EXACT issue, and had to replace a BRAND NEW belt to get it to stop.

In RARE cases I have had them come in and everything checked out fine, and the only cure was to remove the sexy multi-criss-cross pattern belt and put a standard factory style plain old ribbed belt on it and THAT cured it.

I'll bet since this car had an impact, you do indeed have a pulley misalignment issue, even if ever so slight.

Hope this helps.

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Apr 20, 2008
Charlotte, NC
Bump on the mis-alignment.! There's a pulley that's just a hair out. That will make a belt squeak/chirp.
It's probably NOT the tentioner or a pulley on the back side. My guess is the AC compressor pulley. Even though your air might be working fine, the pulley might be a tick off due to a worn clutch.
Fords are notorious for belt noises (and power steering pumps). That's why they don't call them Toyotas. Don't get me wrong, I have 2 Fords, and 2 Nissans, LOL.!