Skip the auto shop - Our mechanics make house calls

Q: Brakes hiss when I use them

asked by on

The ABS light has been on for a few weeks in my 2007 Camry V6 that I have driven for around 104,000 miles, and there's a hissing sound when I apply the brakes. I had my brakes and rotors changed last week by my mechanic friend, and I still was having the same issues. Today, the brakes lost power and it's like having old school manual brakes. Help, please.

Well, it sounds like you may have a vacuum leak coming from the brake booster. I definitely recommend you do not drive the vehicle until you have an independent mechanic look over it, as this is a major safety concern. Typically when you will hear a hissing sound from applying the brakes, or if you hear the sound but the hissing noise goes away when the brakes are applied, it is a very good indication that the diaphragm in the brake booster is failing. The diaphragm allows air to escape the system and thus makes it harder to apply the brake pedal when it is failing. In addition to this, a bad or failing brake booster can be a symptom of another hidden problem, which is known as a leaking master cylinder. Now these two issues don’t always go hand in hand, but they often can and a certified technician will be able to determine if the master cylinder is leaking by separating the master cylinder from the vacuum brake booster and inspecting the cavity in the vacuum brake booster for signs of brake fluid. Brake fluid can eat away at and break down the diaphragm inside the vacuum brake booster as well. Before a repair is attempted, a diagnostic scanner is used to communicate with the ABS computer to determine if the warning light is related to this primary concern. If it is the case, the diagnostic scanner is used to clear the code from the computer and you can have the power brake booster is replaced. If that is not the case, further diagnoses will be needed to identify the problem.

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: I'm trying to figure out if it's my transmission or axle (or both)

Hello. Typically an axle will not cause this unless it completely broke. If that occurred, you would have had an extremely loud noise followed with a grinding and knocking noise every time you tried moving the vehicle. It sounds like...

Q: Car takes time to start

In many cases, a failing sensor can cause an extended cranking time or multiple attempts to get the vehicle started. The problem may be difficult to track down. Have an experienced automotive technician, such as one from YourMechanic, inspect the...

Q: Brake issues

With the engine off, pump brakes several times to deplete the brake booster assist. If you disconnect the front brake line at the master cylinder and have assistant push brake pedal down slow until it's to the floor. Keep your...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...