my car is making noise like if there is air leaking its coming from behind break pedal ( i think) when i press on the break pedal all the way the sound dissapear, and when i press on break half way the sound becomes lower, anyone know whats could be causing this noise and how to fix it?
the car works and drives with no problems but the sound annoys me.
the car is a 1999 mercedes ML430.
thank in advance.

 

it turned out to be the brake booster.