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Squeal when accelerating

Hi all,

I couldn’t find an already open topic that was a similar situation hence the new thread, apologies if its in the wrong place. My car makes a squeal whenever I accelerate, I assumed it to be the fan belt (70,000 miles) so I got that replaced however the squeal is still there. The car has an auto tensioner so its not that and its not the timing belt either. I just tried pressing the gas with the car stationary and turning on lights, A/C etc and there was no sound. Its not a tire or brake problem either, it only happens when I give it gas. The car is a Mazda 2 3rd generation


We are happy you started your own thread, (wish everybody did) this way all replies relate to you. :smiley:

I’d be willing to bet your auto tensioner is wore out and needs replacing


While tensioner failure at 70k miles is a bit early, it is the most likely source of this problem.

It is likely the bearing for a pulley on the drive belt. The tensioner pulley is certainly one possibility. If you want to evaluate it yourself, take off the drive belt and spin all the pulleys. They should spin freely and silently. Any that don’t have problematic bearings, and should be replaced.

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It is going to be the auto tensioner, or the idler pulleys. The tensioner also has an idler of sorts but it is usually just part of that assy and not called an idler proper.

I lucked out one Sunday afternoon. The idler pulley on my 1999 Civic was squealing - it was a little rough running when I turned it, so I figured that was the source of noise. I took it to NAPA for a replacement. They did not have a new pulley in stock - no surprise. But they had the correct bearing and pressed it into place while I waited.

Yes report back after replacing the tensioner and checking the pulleys.

Hi all,

Thanks for all the replies so far. Based on the advice so far it would appear to be a pulley or the tensioner, just wondering if I take the belt off would it be fairly obvious which one needs replacing? If I can’t really tell, which should I replace first based on likelihood of failure?

Thanks again

Replace the tensioner first unless you see bent or damaged pulleys.

Once the belt is off you rotate and you try to rattle all the pulleys. Any graininess or play is a potential trouble spot. Also flex the tensioner lever arm - is it smooth in its movement? Any squeaking? Any dings or cracks in the pulley flanges?

At this point I won’t venture a guess on just where the problem lies, but I would hope for an idler pulley or a tensioner and not an AC compressor!

I don’t think it’s a pulley or tensioner.

If it were, it would still squeal whether the is vehicle moving or stationary when the accelerator is pressed.

What I would try is, open the hood, start the engine, firmly step on the brake pedal, and shift the transmission into gear.

With a helper standing along side of the vehicle, blip the accelerator to see if the squeal can be recreated while the helper watches for any unusual movement of the engine because of a broken motor/transmission mount.


Good and important point, Tester. I missed that it doesn’t happen with the vehicle stationary. Time to reset the speculator.

You hear a high-pitched squeal when accelerating : If you notice a loud squeal when accelerating , especially if your car is just warming up, it could be that you have a loose or worn fan belt. Usually if your fan belts are worn, it could mean your timing belt needs replaced as well.

I would first replace the belt itself… then move toward tensioner and or idler pulley. None of these components ever got a rest here so…if and when I replace a tensioner I also do the idler as well and if the belt is old…it becomes my spare when I replace it with a new belt.

Your belt may be the culprit as they do stretch and the tensioner only has so much ability to take up that slack.