Skip the auto shop - Our mechanics make house calls

Q: I hear a hissing sound when driving, and it only stops right after applying the brake pedal.

asked by on

I would just like to know the problem, and if I have to replace any parts. Thank you.
My car has an automatic transmission.

A: A likely cause of the hissing sound is a le...

A likely cause of the hissing sound is a leak in the atmospheric valve within the power brake booster. The reason the sound ceases when you apply the brakes is because the vacuum valve within the booster closes upon pedal application, thus cutting off the air flow into the booster through the atmospheric valve where the hissing noise is being generated. If indeed this is diagnosed as the cause, in an examination by YourMechanic, the recommended fix would be to replace the brake booster. However, other sources of vacuum leaks would have to be ruled out as well. If you desire this to be inspected by YourMechanic, please fee free to follow up and request a hissing noise at brake pedal diagnostic.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Got fire to coil, none to plugs can't figure it out?

If you got spark out of coil but not getting spark out of the distributor then your distributor cap and rotor are not passing the voltage from the coil to the plugs. Replace the cap and rotor.

Q: hey good day. im joey from the philippines. can you help me out. i would really an opinion about the problem in my car. my honda c

Hi Joey. Unfortunately, it's hard for us to provide you the correct diagnosis of your issue for two reasons. First, we don't offer services or repairs in your country, so it's impossible for one of us to come to your...

Q: I have a collapsing lifter problem on 2009 2.2 cobolt sedan , depending on where motors stops on shut off. Can this be adjustment

If a lifter will not hold pressure and tends to bleed down over time, then the lifter oil relief valve is stuck open allowing the leak down. Depending on what is plugged in, the lifter may not be able to...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...