Brakes are a whistling.. booster?

By the sound in the video, pic of the dirty engine along with you stated that it started while offroading, I'm convinced that it's not the booster. If you have a pressure washer, I would jack up the front and pull the tires. Spray on simple green and pressure wash the engine and front suspension/brake system to rid of all mud/dirt. Un-install the pads and relube the components of the braking system(pins, backing plate). It sounds like there's lack of lubrication that's making the noise. It won't make the noise if the tires are not rolling so just pumping the brakes won't replicate the noise.

 

Hahah yeah she's a dirty girl. I use it!
I off-road frequently, go to my cabin in Utah, and hit a lot of dusty trails in Vegas.... I don't think it's that bad under the hood. LOL.

You are right I did do a quick power wash yesterday, sprayed off the tires, and took apart and cleaned the brake system. Then I re-added synthetic brake grease everywhere and put it back together. I haven't drove much since then but I didn't hear the sound for the little time I did go.

We'll see.

 

Welp.. it's back. What the actual F.

Driving around town I'm fine. No noise, no squeeks, nothing.

Go anywhere (on or off-road) where I have to brake excessively, it starts whistling like a choochoo train. Something must be wrong somewhere. But it ONLY happens under heavy use.

Thoughts

 

how thick are the pads?

 

Something I’ve seen cause noise is glazed braking surfaces. The pads, shoes, drums, rotors could have a polished shiny look. It can be knocked off easily. If it’s the pads I put them face down on a flat concrete surface and give it a little scrub. The other 3 I use some emery cloth to scuff it up a bit. It doesn’t take much effort to do evenly. On the drum and rotor surfaces I go 45 degrees instead of along the same line the friction material contacts. Then a brake cleaner wash down. You might think it would cause uneven wear. I’ve done this multiple times and never had an issue.

 

pads are plenty thick and fairly new. Were fine for several months before this started.

 

Can anyone help diagnose this problem. An odd sound coming from the master cylinder area. Happens when I brake. But its not a hissing type sound. More like electric to me. See attached vide.
https://youtu.be/yizi8K9G5rI

 

There is an electric motor that spins a hydraulic pump on the master cylinder of your truck. Its normal.

 

So no worries at all!?! Has this been happening for 10 years, and I have never noticed this sound?

 

Possibly, did the sound change recently? Give this a try, truck fully off key out of the ignition pump the brakes multiple times. There will be a point where the pedal feel COMPLETELY changes. This change is due to the pressure / fluid being completely depleted in the accumulator of the master cylinder. Put the key in the ignition and turn to on but dont start the motor. You will hear the electric pump spinning to build accumulator pressure back up. Depleting the pressure completely often fixes weird sounds with a trapped air bubble etc.

 

Thanks man - I'll def. give that a shot, and keep u posted.