Skip the auto shop - Our mechanics make house calls

Q: Brakes go to floor

asked by on

I hear a hissing noise when brake pedal is depressed and slowly goes to floor and does not stop truck. But when I depess it fast it works as before. Master cylinder-no leaks. What do you think?

My car has 70000 miles.
My car has a manual transmission.

One of the most common causes of the brake pedal going to the floor is a loss of brake fluid. Generally, this is easy to detect due to the fact that there is usually brake fluid leaking on the ground underneath the vehicle. The brake booster is a mechanism that uses vacuum pressure to take the force being applied to the brake pedal and amplify it. If the booster is bad, then the full amount of force needed to activate the master cylinder and pressurize the brake fluid isn’t going to be there.

Another possible cause for this may be a failing master cylinder. The master cylinder is where the brake fluid is compressed creating the necessary hydraulic pressure the braking system needs in order for it to stop your vehicle. When the master cylinder fails, this may cause a loss of hydraulic pressure which will usually also cause the brake pedal to go to the floor. I would recommend having an expert from YourMechanic come to your location to diagnose your braking system.

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: Anyone have a acurate duagram for a 1993 nissan altima gxe serpentine belt placement ?

Your vehicle use a two belt system as depicted in this diagram. If you desire, a mechanic dispatched by YourMechanic can re-install the belt and, as is required during any belt replacement, inspect all of the rolling elements driven by...

Q: 4 wheel drive will not engage.

Hello. There appears to be three different locations for the control module depending on the chassis. The 4wd control module will either be found behind a kick panel on the passenger side, inside the dash, accessible by opening the glove...

Q: Explorer turns over but wont start.

Hi There, It sounds like you may have a fuel supply problem in getting the proper amount of fuel to the fuel injectors. As you know, when you turn the key to on, the fuel pump is activated and the...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.