My Highlander squeals every time when I start it. A few times it has continued squealing while driving until I stopped and restarted it. My belts are fine, they are practically brand new, and I have had them checked. Is there anything else that could be the perpetrator?
If the battery is really on its last legs, the alternator will work extra hard to recharge it. Hard enough to slip your new belts and squeal. Same for a failing power steering pump. Work the steering wheel back a forth and see it the squeal gets louder. If so, the pump may be failing. Or a failing AC compressor. The AC is easy to check, turn it off, does the squeal stop? If Yes, AC compressor needs service.
You could have a belt tensioner pulley that is failing. They make a heck of a squeal. I’d put my money on the tensioner.
The only time I had a squeal the alternator belt was loose; the alternator had moved a little. Forcing it back out, which took sticking in a scrap of wood and bashing it with a mallet, then tightening the screw, then working the wood out, fixed it - that was 14 years ago; hasn’t squealed since.
There’s a belt dressing spray that didn’t make any difference for me.
The alternator/air conditioner belt is not tight enough. If this is a 2007 or older with a V-6 the belt has a manual adjuster, when the belt was installed it was not set tight enough.
I’m presuming this sound goes on beyond the cranking period. If you are certain the accessory belts and their adjustment are not the problem, other things that can squeal during start up, then the sound goes away, are the power steering pump, alternator, water pump, and any associated pulley bearings. Timing chain/belt and the components in their path can cause this too, but less likely.
I’ll add my Corolla makes a little squealing noise on cold starts that quickly goes away, and it is caused by the power steering pump. Ask your shop to use a mechanics stethoscope to narrow down where the noise is coming from.
U say tensioner pulley. Could be any pulley. Idler puller too. Or tensioner itself. Most tensioners look good. How do u check the tension it applies?