whistle noise coming from under dash when applying brakes

[blackbox19]

I have a 2013 and notice here lately that when I put foot on brake there is a whistle noise coming from the petal area.
It does not sound like air coming out of something but more of a hydraulic fluid passing thru a slightly open valve. I came from the Aircraft field and on some of the hydraulic systems you could hear a noise similar due to a unseated valve.

If I press hard it will do it and it I set there hold slight pressure if does it worse. Light setting at a red light.

It does not do it all time and the brakes seem fine otherwise. IF need be I will get a video of the sound to help pin point whats going on.

 

[Dannydean]

If I had to guess, I'd say your brake booster is bad. Does the engine stumble a little when you apply the brake while sitting still?

 

[blackbox19]

Nope.. Engine runs normal..

 

[blackbox19]

here is a video of the sound.

 

[SnowDrifter]

That's a good whistle ya got going there.

Sounds like the brake booster is work out. It's a vacuum operated system.

Un plug and cap the vacuum line going to the brake booster, stomp on the brakes to verify. Dont drive the vehicle when doing this, I just want to isolate its not a bizarre ground loop or something created by the brake switch.

If there's no sound, then you've verified the booster is bad.

 

[Aquarianking]

I’m going through the same with my 2001 Yukon xl