The brake booster is one of the main braking components that controls the power braking system in your car. If the brake booster is going out, you will probably discover it fairly quickly because your brakes will develop problems. You may experience a mushy brake pedal, an overly stiff brake pedal or begin to hear whining and hissing noises from your brakes.
If you hear a whining or hissing noise when you press down on the brakes in traffic, your brake booster may be going out. This may be caused by a hole or other problem with the vacuum line attached to the brake booster. When you press down on the brakes, the air is forced through the vacuum line. If there is a hole in it, air will be forced through it, making the hissing or whining noise you hear.
Low Brake Pedal
If you are having a problem with the vacuum on the brake booster, the brake pedal may go closer to the floor than usual when the brakes are pressed. The vacuum cannot seal the brake system properly, and this symptom of a bad brake booster may accompany the brake whining or hissing noises.
The brake booster is a primary part of your car's power braking system. Essentially, the booster is the power part, using vacuum pressure to assist you in depressing the brake pedal and making the car stop. If the brake booster goes out completely, you will not have power brakes. The braking system should still work, but the brakes will be stiff, and the pedal will be difficult to depress unless you have a significant amount of leg strength.