Help with Brakes high pitched squeal...WTF

Have a 06 Tacoma pre runner trd dbl cab 140k miles ..last year started making high pitched noise when braking on and off over a few months now its almost constant when braking slowly. I had new brake pads put on new wheel bearings and a new caliper which was bad. Its still making this super loud high pitched squelling when applying brakes at slow speed. My mechanic doesn't know what it is. Should I spray something on the brake disc??

 

It could be the rear drums...

 

Has he checked the rotors for any significant grooves? If you have semi metallic pads you could have gotten a larger than normal metallic piece in there that's slowly been more exposed hence the increase in noise. You could also have a foreign object like a pebble on the pad face. I would agree with checks your drums and see what's going on back there.

As far as spraying stuff on your brakes, the only thing that should touch them is brake parts cleaner but I doubt that's going to solve your issue.

 

My thoughts too

 

Make sure the hub surface and back of the rotor are free of rust and grit. Using a high temperature brake grease is recommended on these surfaces. Also wire brush and lubricate the sliders as well as apply a thin coast of brake grease on the back of the brake pad even if it has Teflon noise suppressors. Make sure the backing plate wasn't accidentally bent and rubbing on the inside rotor surface.
The goal is to eliminate all sources of potential harmonic noise. Assuming you have properly identified the front brakes as the source of the noise these are the most likely causes of your problem.

 

a bent backing plate has a tendency to make noise under a slow breaking condition . Have seen this a couple times as well .
For what its worth , give the backing plates a light pry away from the rotors and re-test drive for results .

 

Hey OP - did you ever figure out what the cause of this was? I have the same issue verbatim, but i've ignored it for like a year now. High pitched noise happens 95% of the time at a slow stop (stop sign, right turns, etc), but when i had my brakes checked 2 years ago everything checked out. Also don't have any vibration or issues braking. It slowly became more common until about 8 months ago and it happens almost every time i brake.

I'm going to the garage this weekend to take the wheels off, just wondering if you found the culprit - thanks

 

Having the exact same issue on my 2017 Taco. Driving me nuts!! Toyota looked at it twice. My mechanic looked at it and keeps coming back everything checks out fine. I'm about ready to replace the rear drums and shoes.

 

Try resurfacing the rotors, new front pads, and new drum shoes and probably resurface the drum. I have to do this far too often after off roading due to dirt ruining the rotors and whatnot