Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Brake Master Cylinder

Brake master cylinder

Bad or Failing Brake Master Cylinder Inspection

by a top-rated mechanic at your home or office

The brake master cylinder is one of the most important components found on modern car braking systems. It serves as the main valve that pushes brake fluid through the brake lines so that the brake calipers can squeeze the pads against the rotors. It functions by pushing a metal rod through a cylinder to force fluid through the braking system to the wheels. One end of this rod is attached to the pedal and is actuated when the pedal is depressed. Usually a faulty brake master cylinder will produce a few symptoms that alert the driver that service may be required.

HAVE SYMPTOMS OF CAR TROUBLE?
Get an $80 diagnostic
by a top-rated mechanic at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

1. Abnormal brake pedal behavior

One of the first symptoms commonly associated with a bad or failing brake master cylinder is abnormal brake pedal behavior. The master cylinder is the component that generates all of the pressure for the braking system, and if it develops any sort of problems sealing or distributing pressure, this may be felt in the pedal. Over time, with constant use, the seals inside of the cylinder can wear out and form internal leaks. A bad brake master cylinder may result in a pedal that feels mushy, spongy, or that slowly sinks to the floor when depressed.

2. Contaminated brake fluid

Another symptom of a bad brake master cylinder is contaminated brake fluid. Brake master cylinders use rubber seals which can break down and wear out over time. When they do, they can contaminate the brake fluid and will turn it dark brown or black color. Aside from contaminating the fluid, a brake master cylinder with worn seals will also not be able to hold brake pressure as effectively and may also result in a mushy pedal or one that slowly sinks to the floor.

HAVE SYMPTOMS OF CAR TROUBLE?
Get your car fixed at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

3. Check Engine Light comes on

Another symptom commonly seen for newer vehicles is an illuminated Check Engine Light. The braking systems on newer vehicles may have brake fluid level and pressure sensors installed in the master cylinder. These sensors are meant to detect any problem with the vehicle’s brake fluid pressure, which is generated by the master cylinder. If they detect that the pressure has dropped, it is possibly due to a problem with the master cylinder.

As the brake master cylinder is essentially the heart of the braking system and vital to reliable brake operation, it is an important component to the handling and safety characteristics of the vehicle. A vehicle with a bad brake master cylinder will have inoperable or compromised brakes, and therefore will be unsafe to drive. For this reason, if you suspect that your brake master cylinder is having a problem, have the brake system diagnosed by a professional technician from YourMechanic to determine if it the car needs a brake master cylinder replacement.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...


Related questions

Q: Car is reading trouble code PO136 01/01

Hi. There could be a couple of things going on here. There are multiple oxygen sensors on your car and sometimes what we think bank 1 is may not be and the wrong oxygen sensor is replaced giving us the...

Q: Heavy vibration when braking above 40 mph. Also vibrates in the steering wheel

This may be a variety of things, such as wheels and tires out-of-balance, poor alignment, worn or failing wheel bearings, worn or failing control arm bushings, or worn or failing suspension components. A wheel bearing will usually fail due...

Q: Brakes don't work good in my 1996 Honda Accord

Hi there. From what you are explaining it sounds like there is a leak in the system. The brake fluid should not be going down at all unless there is a leak. If you are losing brake fluid and there...