Posts Tagged: brake booster

Hissing sound from brakes

What causes a hissing sound from under the dash If you notice a hissing sounds from brakes while inside the passenger cabin, that’s the sign of a failing vacuum booster. The vacuum booster uses engine vacuum to increase braking power. The booster uses a rubber diaphragm and a push rod. The rod is connected on one side to your brake pedal and the other side pushes the master cylinder piston. When the engine is running and you’re not applying the brakes, engine vacuum is applied equally to both side of … Read More