Skip the auto shop - Our mechanics make house calls

Q: Brake pedal sinks

asked by on

Brake pedal sinks, I added fluid, it wasn't very low.brakes was good before. It keeps taking fluid. I haven't seen any signs of leaks at calipers, master cylinder, or under dash. Pedal will feel good when sitting if I pump it. Once key is turned it sinks. And yes my check engine soon light comes on shortly after driving. Could this be the master cylinder?

My car has 82000 miles.
My car has an automatic transmission.

A: This is a sign of a potential vacuum leak i...

This is a sign of a potential vacuum leak in the brake booster. When there is not enough vacuum in the brake booster, this will cause a hydraulic pressure drop resulting in a soft brake pedal. If you'd like, a certified YourMechanic technician can come to your location and help you with a Brake pedal is lower than usual Inspection to confirm that this is the issue, and also help to perform a Brake Booster Vacuum Pump Replacement to repair this issue.

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・Save up to 30%

Get a quote

What others are asking

Q: Heater blows cold air

Hello. The Heater/AC control panel utilizes vacuum (from the engine) to actuate the hot water control valve - regulating heat from the heater. A vacuum leak, bad hot water control valve, or the heater control panel itself may have failed....

Q: how to tell if my mass air sensor or my tps is the problem?

You did not state the model and size of engine you have? Most Nissan distributor engines have a base timing between 13 and 17 degrees BTDC (before top dead center) at 700 to 800 RPM. If you have the timing...

Q: How do I inspect the tires for tire wear?

Inspecting the tires is an essential step to keep up fuel economy and prevent premature tire wear and replacement. To inspect the tires. Remove any glass or stones wedged in the tire tread. Check to see if the tires...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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...