New user squelling sound from master cylinder?

New user guys really enjoy the site always good useful info. I have a 2001 double cab 4x4 and recently have a squelling issue that sounds to be coming from master cylinder area. Its a constant squell till I push on the brakes and goes away only to return when I let off the brakes. I can kill the engine and still hear it for a brief time then it stops. Any help would be greatly appreciated. Thanks

 

Sounds like a problem with the booster. Check for leaks.

 

Thanks I will look at it

 

Mine is squealing too. If I put pressure on my master cylinder by leveraging it up or down, I can change the pitch of the squeal or even make it go away. I believe my leak is internal to the booater. $500, yea.