Brake whistle (sometimes)

Hey guys,

Lately, I've been experiencing an odd "whistle" coming from the brakes, but ONLY during excessive use like while off-roading for extended periods, or going down the mountain.

This doesn't happen around town. I have new pads and rotors, and I've removed them to check for rocks and such, too. If this was a rock or an issue, I'd hear it all the time. I do not.

Instead, when I hit a trail or go off-roading it starts to happen near the end of the trail after heavy usage going back down the side of mountain or something. I have a 2011 TRD, so there isn't a brake booster. It's an electric system, not hydraulic. When I first start to tap the brake I get a super loud "whistle" noise that's pretty sharp and high-pitched. As a press the pedal further to brake more, it goes away. It's only the first inch or so of pushing on the brake.

Any ideas? I'm going to try a full fluid flush and bleed next, but I've checked a bunch of things and I'm running out of thoughts. haha.

Brakes work fine... they just whistle going down the mountain.

 

How new? Sounds like new pads breaking in to me.

 

The pads are like 4-5 months old

 

Is it a whistle like a teapot, or more like a high-pitched electronic noise?

If it's a whistle like a teapot, I have no idea, but if it's the high-pitched electronic noise could be that your electronic brake booster pump is wearing out.

Not a fun fix, the only repair I'm aware of is full replacement and I believe that unit is in the neighborhood of $1,200 to $2,500.

The other option is to change to a vacuum assisted brake setup like folks do for 1 tons but you will lose A-Trac and possibly ABS/VSC.

 

Haha damn. Yeah it's like a teapot. Let me see if I have a video of the noise.

Video found.
https://youtube.com/shorts/wggmTBvtt-I?feature=share

 

Definitely sounds more like the low pad material squeelers to me. I'd check they're not bent or installed incorrectly or just flat out remove them entirely, I usually clip the noise maker arm on mine.

 

Yeah.. agreed, but they're not low.

I'm going to just get stock OEM pads and do a fluid flush and bleed. See if that does the trick

 

Sometimes brakes squeak and it's not necessarily a problem...under light pedal pressure, it could just be pad vibration. Did you grease the backing plates/shims? What happens if you partially engage the parking brake while moving?

A couple of weeks ago I was convinced a brake-related noise was coming from the front...in my case the noise went away when I applied the brakes. After investigating, I discovered the pins that engage the hold-down springs for the rear shoes had rusted away, and the sound I heard was the springs and retainers tumbling around in the drum. Easy to fix, but it took me a minute to figure it out.

 

Sounds to me like pad to rotor contact/vibration.

Some pads have a shim riveted or clipped on the back side to help counteract this noise. I’ve tried that goop rubber glue stuff you slather on, didn’t work for me.

If your new pads came with no shims, you might be stuck with the noise until you swap them out.

Sometimes the pads will get a glazed appearance. If you knock the glazing off with some emery cloth or just rubbing them on a rough cement surface. Just keep it as flat as you can. Use emery cloth with a wood block. Sometimes it’s a temporary fix, sometimes it’ll last.

 

Not saying the pads are low I'm saying the squealer may be making contact, if a rock or mud gets jammed in there it can bend it and make contact before the material is worn down heat from breaking causes it to expand just enough to be *REALLY ANNOYING* played that game before hence why I clip my squealers and just check them often.

 

I'll check the squealer again but I've already removed the wheels and inspected the pads and everything.
As for other comments, yes I have shims (backplates), pins, and I tried the anti-noise stuff after putting them back together the first time I heard this noise.

Could this be one of the brake pistons or something? I think I'm going to get a wire brush and clean the HELL out of everything, replace pads, and change fluid, then see how things go.

 

Doubtful, I've had a piston seize on me and it didn't make any more additional noise though you may be running a different material than I was, but if you did have a piston seizing you should definitely be able to feel it as a pulling sensation in the wheel when braking.

If one of your pots is seizing, the only real good fix is to replace the entire caliper.

 

Yeah, no pulsing. The brakes feel and sound fine most of the time. Even going down a trail they feel fine, just start to whistle after a lot of use... That's the most confusing part, they don't always make noise.

ONLY during heavy usage situations.