Whistleing brakes on 2002 Volvo V70 XC

I have a hissing sound and whistle from (a braking) component. Reason, when I step (press) on the brake pedal the noises stop. Any clue as to what this is. It sounds like an air leak.

by in Lititz, PA on February 28, 2011
Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
1 answer
ANSWER by , February 28, 2011
brake booster could be leaking