Brake System Whistle when Pendal Pushed Hard

[RFIRE]

My 2007 Ford Edge just started to whistle when I brake hard, even if the vehicle is not moving. It only starts with the pedel pushed in so far and then goes away when pushed further. No noise when the motor is off.

Do you think it is the master cylinder or the power booster? The whistle comes from that general area.

Richard

 

[Astro14]

Booster...sounds like a vacuum leak...

 

[parimento1]

I have the same problem on my Taurus. The booster has a small leak in it. Mine loses pressure almost immediately after shutting the car off. I haven't gotten around to fixing it.