Periodic Squeal Under Hood

[Neuner]

I'm at a loss in trying to figure out an intermittent squeal under the hood and hoping for some good suggestions based on experience.

I've tried to get it on video with no luck. Seems that every time it happens, I'm not in a position to stop and open the hood.

What I know:
- '99 with 315k
- Timing belt replaced at 283k
- Serpentine belt recently replaced
- Master cylinder recently replaced
- Seems to happen more when cold but will still happen after running a while. Random or I at least can't find a cause or reason for when it happens.

The one time I was able to get the hood popped open while the engine compartment was squealing, I heard the noise more towards the rear of the engine and not the front. Seems I heard it more near the master cylinder area.

It's high-pitched but doesn't seem like a bearing. It's not constant or periodic.

Thought it was the serpentine so I replaced it. Was quiet for a bit but then acted up again. Then I thought it was the failing master cylinder as it seems to come from that area while driving. It's since been replaced and the squealing remains.

This is my wife's daily and it's driving her crazy. Really hoping to figure it out for her so appreciate some insight.

 

[Exiled]

Idler pulley would be my first guess given the mileage. Not discounting the brake system but I would check that idler pulley first.

 

[2001LC]

Assuming new OEM brake master, helps rule it out.

 

[Neuner]

Thank you. I'll give the idler a try.
Is Dorman OEM? I'm pulling up 419-684

 

[2001LC]

Thank you. I'll give the idler a try.
Is Dorman OEM? I'm pulling up 419-684

No!

 

[2001LC]

For idler I use Toyota, they last longer than any aftermarket I've ever found.
For tensioner, I will replace just the bearing, unless tensioners return spring recoil is bad or I'm doing a time belt service.

See: under "Drive belt and pulleys:" in my Master thread, in signature line.

 

[2001LC]

These two Serp belt (fan belt) pulleys' bearings, are most common squeal. The belt well also squeal, when wet, when past useful life.

So will alternator (don't get it wet), often heard just before failure. They fail more often, when #1 under shield missing.

We also need to check the fan clutch.

I find more, while washing radiator fins. I correct bearings, and wash fins again. If squeals again replace Serp belt

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

 

[Neuner]

Got OEM Pulley.

What should have been an easy replacement turned ugly as it appears it was replaced before and they had stripped the threads without repair. I was almost able to undo the bolt by hand. Old pulley didn't seem to be in bad shape. Still appeared smooth and didn't make any noise or have any kind of grind to it.

Got the new one installed tight, and so far, the missus is happy, reporting no squeal. I'm not celebrating yet though as I've learned to give it time.

 

[Mike NXP]

Got OEM Pulley.

What should have been an easy replacement turned ugly as it appears it was replaced before and they had stripped the threads without repair. I was almost able to undo the bolt by hand. Old pulley didn't seem to be in bad shape. Still appeared smooth and didn't make any noise or have any kind of grind to it.

Got the new one installed tight, and so far, the missus is happy, reporting no squeal. I'm not celebrating yet though as I've learned to give it time.

fingers crossed, it sounds like you sorted it out, the dorman pulley + lack of torque sounds like a problem for sure. Assuming your tensioner felt good when you took the belt off, had plenty of spring back ?

If the noise comes back you'll just need to remove the belt and start checking components one by one. I chased a squeal for a while before realizing it was my fan bracket, which is buried kind of deep in there and many others have reported the need to replace w/ higher mileage vehicles