Serpentine belt noise problems - potential fix

Hello everybody:

I posted this answer in a couple of Mazda forum threads, but I think it could be of general insterest to others as well.

O.K. Guys, here's what I found out:

My daughter brought her 98 Protoge LX over because her A/C compressor had "blown up" internally, locked and fried the belt. (this belt runs the A/C and power steering). I had her bring it over and installed a new belt and told her not to turn on the A/C until I had a chance to locate a new compressor and get it installed. I ran one down on E-Bay and had her come over and I installed it. After all the hoo-ha of swapping the compressor and re-charging the A/C system and getting it all working, low and behold the belts still occasionally squeak or "rumble" intermittently. The only way I could get the darn things to quiet down was to tighten the belts WAY TOO TIGHT!!!! Then there was less squealing, but more squeaking and "rumbling" even when there was no load on the belt. Upon messing around with it for awile, we found that the alternator belt (drives the W/pump also) was also squeaking intermittently when the A/C was on or the headlights were on due to the additional electrical load on the alternator. Once again, the only way to eliminate the majority of the squealing was to over-tighten the belt to what seemed to me to be near the point of breakage.

After all this, the belts still squeak and rumble, sometimes even when not under load. ?????

In desperation, I removed BOTH belts from the engine and took them up to the bench to check, I found no apparent defects, cracks or problems, which was logical because they were both essentially new. I went back to the car and was leaning over the fender contemplating all this when by accident I happened to shine my trouble light directly on the bare pulley on the w/pump. Low and behold, in the bottom of the V-grooves in the pulley itself, some sort of debris (melted rubber/dirt ??? ) was packed into the bottom of the grooves. I got one of my pointed probes and started scraping the crap out of the grooves. It was amazing how much junk I could get out of the V-grooves. Since that particualr pulley was for the water pump, for ease of cleaning, I removed it from the water pump. Back at the bench, I spent the better part of 15 minutes scraping the crap out of the pulley grooves. Once done, I went to the grinder and used the wire brush to completely clean out the grooves.

Returning to the car, I checked the double pulleys down on the crankshaft and found the same condition (only worse). This time rather than removing the pulley from the crank, I simply started the engine, and while idling, I CAREFULLY inserted my "hook" probe into the pulley grooves while spinning. The crap simply flew out of the grooves. Upon looking at what fell on the floor, it looks like pieces of a black rubber band, and and small chunks of rubber mixed with dirt.

It was harder to clean out the grooves on the alternator pulley but I did the best I could with the alternator still on the car, I think I got nearly all of the crap out of the grooves.

Low and behold, after putting it all back on the car and starting it up. NO SQUEAKS. This is even with both belts tightened WAY loose. (even with the A/C AND headlight on).

So, you might want to check this out. It sounds like you may be tightening the belts so much in an attempt to get them to quit squeaking that they are breaking prematurely. It's what I had been doing to try to stop the noise.

I've been working with cars for over 50 years. I was a line mechanic in the Cadillac garage and am restoring two cars presently, but I gotta admit, this was new to me... I have fought with serpentine belts on all my cars. None of which seem to work correctly. Even when I replace belts and tensioners, they still chatter and squeak. I am going to check them for this problem, which I think it may be the root of all this heartburn.

I would tell you that this condition is HARD TO SEE, On my daughter's car, the pully V-grooves ARE NOT rounded in the bottom of the groove. The "V" groove should have a "sharp" bottom. If the grooves are not COMPLETELY clear, then the belt will ride over the debris in the bottom of the groove and not grip the grooves properly.

So get in there and check them closely, sorry, it's not easy to get the junk out of the grooves either. It is darn near hard as a rock.

Do all this, install new belts and tighten them reasonably, and I think you might find a fix for your problem.. I did.

We were all better off with good ol' V-Belts....

I just finished working on my 97 ford probe's alternator belt, it snapped, so i had to replace it. I'm pretty sure the protege angine is very similar if not identical with mine and yes, the puleys filled up with a derbit, rubber and string from the old belt! It just tightend around the puley and i had to scrape the pieces out. I can see somebody not checking for left over belt pieces in the grooves and just putting the new belt over that crap. I'm pretty sure that with the modern "gator grtip" designe belts it would eventualy distribute itself to the other pulleys. - just thought to add this observation to what might have been those derbits

Perhaps you should change the belt more often so it does not have a chance to deteriorate and clog up the groves in the pulleys. If belts get oil on them they will soften up over time causing the belt material to transfer to the pulleys causing the condition that you described.


Just my :2cents:

Here is a good one. I had to change both belts on my other ford probe, '97 2.0l 5 speed as well. on this one there is no oil leak over the belts as on my other one so the belts were just old and making noise on engine start up, all the pulleys are nice and clean. the belt seems to be be put on right and it is the right size belt :) . Well here is what is strange, the ac/ps belt still makes a lot of noise for the first 20 seconds when ever i start the engine (hot or cold) and even sometimes out of nowhere when car idles with AC on. it seems to have nothing with to do witt the tightness of the belt since id does the same regardless if i tighten it or leave it loose. I would blame the tensioner pulley bearing, but this car does not have one?! Any ideas?

It is a pretty common thing to find crap in the bottom of pulley grooves. The belts put off a rubber 'dust' which sometimes hangs out and builds up on the pulley. A pocket screwdriver and a few minutes of work should get it all out. Locked up pulleys or accessories don't help much either ;)

And what did you find out?

The material is called belt pilings and is one of the most common causes of belt squeaks. Like RahX said, always clean the pulleys when you replace your belts. Wire brush, pocket screwdriver, etc. Some brake cleaner and compressed air help. If it is a GM product make sure the power steering pulley is flush with the pump shaft.