Diagnosing a brake noise, need help..

[kgc]

I also had this problem. Subaru dealership said it was brake dust accumulation and blasted everything with cleaner. Sound is gone for now, but maybe it’s a temporary fix.

Perhaps there a mod we can do to blow the dust off the brakes continuously...

[guybo]

It's probably the slotted rotors being noisy- do you feel any vibration? How old is your brake fluid?

[Tcoat]

Originally Posted by kgc

I also had this problem. Subaru dealership said it was brake dust accumulation and blasted everything with cleaner. Sound is gone for now, but maybe it’s a temporary fix.

Perhaps there a mod we can do to blow the dust off the brakes continuously...

You could hook up a 100 psi compressor with all the lines and about 40 outlets that pulse individually to blow off each section of the calipers where dust builds up.
Or...
You can have your brakes serviced/service your own as per the recommendations in the service manual

[kgc]

Originally Posted by Tcoat

You could hook up a 100 psi compressor with all the lines and about 40 outlets that pulse individually to blow off each section of the calipers where dust builds up.
Or...
You can have your brakes serviced/service your own as per the recommendations in the service manual

The noise came back the next day. I think there is a different underlying issue.

[dutchman1]

So you have a squeal on slow speed stops coming from a specific corner of the vehicle, correct?

If it's barely a squeak and goes away after one stop, it's normal and I wouldn't worry about it. Any more than that on stock pads would be odd.

Warped rotors aren't really a thing. You can have uneven pad deposits on them, or uneven wear/runout, but warping is basically unheard of on modern rotors that have any thickness at all left.

First thing I'd do is jack up that corner of the car, turn the wheel and make sure the brakes aren't dragging at all. If they are, you probably have a caliper or slide pin issue.

Regardless of whether or not the brake is dragging, take off the wheel. Take the caliper off, look at the pads. If they feel smooth and look shiny on the friction surface, they're glazed over and need replacement. If they're glazed, replace the pads and make sure you lube the slide pins. Dry slide pins are one of the most common causes of glazed pads, pad noise, and/or uneven pad wear. Use grease, not anti-seize. Anti-seize is a great high-temp lube, but a terrible high pressure lube. It'll just squeeze out from between the surfaces it's supposed to be coating.

While you're at it, borrow a dail indicator and check your rotor for even wear. Anything more than about .005" variance is cause for replacement or resurfacing. You're going to have some variance, some from play in the wheel bearing and some just because things never wear perfectly, but it shouldn't be much. If your rotor measures out fine, and there are no grooves you can catch with your fingernail, you don't need to get them resurfaced. Going from stock to TRD pads or stock to new stock pads there won't be a need to remove the old pad deposits.

Also make sure nothing is stuck between the little dust shield and the rotor, and that the shield isn't bent into the rotor or anything like that.

Bed your new pads in properly. If you don't you can get vibrations and other issues from uneven material deposits.

You should be good at that point. If it happens again, and you made sure to lube the slide pins properly, I'd suspect a sticking caliper.