Hissing Noise From Brake Pedal

YOUCANIC • 12 December 2019

Do you hear a hissing noise coming from the brake pedal? The noise may be there constantly, or you may only hear it when you press the gas pedal.

If you hear a hissing noise from under the dashboard that changes when you press or release the brake pedal area, it most likely is a brake booster that is failing.

Symptoms

  • Air Noise from the brake pedal
  • Hissing sound when applying the brakes
  • Brakes sound like air is coming out. 
  • Brake booster problem hissing sound
  • Whoosh sound when you apply the brakes

Common Cause

Brake Booster

hissing noise from car when braking due to bad brake booster

Do you hear a hissing noise when you press and release the brake pedal, even with the car fully stopped? Does the hissing noise sound like this? 

It may sound like air is coming out when you press the brakes, but in reality, air is being sucked in. The noise is typically caused by a leaking brake booster. A brake booster has a diaphragm inside on one side of it the vacuum created by the engine.

The brake booster has a hose that is connected to the intake manifold of the engine. The vacuum created from the engine makes pressing the brake pedal easier and assists you so that you don't have to press the brakes as hard to stop the car. 

air noise when pressing brake pedal

Typically when you hear the hissing noise from the brake pedal you should check the brake fluid as well just to be sure you are not losing any. In most cases, you don't lose any brake fluid.

The noise is caused by air being sucked via a cracked brake booster O-ring or silencing foam or diaphragm. In some cases, you may notice that the noise goes away when you press the brake pedal or gas pedal. 

Replacing the brake booster will fix this problem. Replacing the brake booster requires some DIY skills so if you don't plan on fixing the hissing noise yourself take your car to a mechanic. 

The brake booster is located right behind the master cylinder. It is the black round tank between the master cylinder and the firewall. 

Don't neglect the hissing sound coming from behind the dash/brake pedal area. If you continue to neglect it, you may lose your brakes while driving which can be catastrophic. 

Brake Pads

hissing nosie when pressing brakes

Brake pads have a wear sensor. As your brake pads wear down, the wear sensor makes contact with the rotor which causes more of a grinding noise when you are braking. You should only hear this noise when you are braking and not if the vehicle is stopped.