Why do I hear hissing when I brake?
Why do I hear hissing when I brake? Hissing. A hissing noise is usually the brake booster leaking air. There could be a leak in the vacuum line, the booster diaphragm, or the master cylinder. A small leak could cause a hissing sound when you press on the brake pedal or let off. What kind of noise does a bad caliper make? Squealing or metallic rubbing noise. If a brake caliper is sticking or freezing up, noises may be heard from the area of the damaged part. Unlike the noises related to worn brake pads (which occur when the brake...