The Unfixable Squealing Serpentine Belt



Here’s the dilemma. I own a 2003 4Runner. A year after purchasing the car, the serpentine belt began squealing. I took it to a Toyota Dealership in the area who replaced the belt and mentioned something about a “belt defect”. Two years later (~3 months ago), the belt began squealing again. So I went to Napa and got an aftermarket belt and put it on myself. . Now three months after putting on another ?new? belt, the thing is squealing like a banshee again (Each time I put a new belt on, the squealing always goes away?but only for a while). So today I took it too a repair shop and say ?the belt is the symptom but there is some underlying problem causing the belts to wear out and squeal?. They call back and say ?the belt is problem, we put water on the belt and it stopped squealing so we know it isn?t a pulley.? I tell them that there is a reason why the belt keeps wearing out and start squealing but they seem to be at the end of their diagnostic ability so I give up.

Here are my hypothesis and questions:

1.) A pulley is slightly out of alignment causing the belt to wear unevenly. Where do I go to have this checked?do they need a laser to check pulley alignments?

2.) The AC unit (or other unit?) is pulling too hard and causing the belts to wear out. Who would know how to check this?

3.) The belt tensioner is not tight enough causing the belt to start squealing once it has a little wear. How do I check this, with a torque wrench?

4.) Something else is causing my belts to wear out and I have no idea where to look. Who could help?

By the way, I called the Toyota dealership today that I took it to a few years ago and they said ?we have no idea but we haven?t heard of any of the problems you are speaking of?. Any suggestions would be greatly appreciated!! Thanks,

Jim S.

defect". Two years later, the belt begins squaling again. So


Of course, a belt will stop squealing when you put a lubricant, like water, on it! Duh! If the belt goes true across the pulleys, look for components which are loading the belt. Remove the belt, turn the various pulleys with hand, or, wrapping the belt around each, and “feel” how easily they turn. To check the A/C pulley: with the belt on, and the engine running, turn the A/C switch on the dash OFF and on. Watch the engine. It it seems to load with the A/C on, the A/C compressor is causing the squealing. Replace the A/C compressor.


I had the exact same problem with a 2003 Toyota 4Runner just after we took delivery. The dealer’s service department changed the belt at least 3 times in the first month. One time, the technician didn’t get the belt on correctly and it pulled out the oil seal. At any rate, when we took it back and were most unhappy, the salesman went in on our behalf and talked to the manager of the agency and the service manager. They replaced the belt tensioner and we haven’t had any problems since. This was 4 years ago and we have gone 50,000 miles since that time with no problems. If you don’t get satisfaction from the dealer, you should call the zone representative.


I should add that the engine in my 2003 4Runner is the 4.0 V6.


As Lt. Columbo would say, “Just one more thing”. I take the 4Runner to an indendent garage for my service work. After I got the belt tensioner issue resolved, I’ve had no more problems and had no need for warranty service. The servicing has all been done by my independent shop.


Just curious, do you think a belt tesioner can be too tight? When I changed the belt three months ago, I could hardly move the tensioner. It took almost all I had to get it loose enough to slip the new belt on. Of course, my hands were wet from antifreeze since I had to take a radiator hose lose to get to it…maybe that was my problem! ANyway, thanks for the input.

Jim S.


You’ve found it: change the tensioner.


I supppose it’s possible, but probably unlikely. I would think that the service manuals that the Toyota service department has would show how much pull the tensioner should exert and a simple instrument could measure this.


I have a 2000 Blazer that’s quick picky about serpentine belts. I’ve tried Napa (Gates?) and Dayco belts. The belts didn’t squeal but were very noisy as soon as I installed them. I’ve had better luck with Goodyear Poly-V belts. This belt is much quieter on the Blazer than the others. They are available at Summit Racing or from Advance Auto (

Good luck,

Ed B.


I doubt that the service manual has the tensioner value of the belt tensioner; but, there’s a way to get the value. The mechanic could test the tensioner by clamping a new tensioner in a vice, turn it with a torque wrench, and compare that value to the old one on your vehicle. What’s so difficult about this, Mr. Mechanic?