Symptoms of a Bad or Failing Brake Master Cylinder

The brake master cylinder is one of the most important components found in modern car braking systems. It serves as the main valve that pushes brake fluid through the brake lines so 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 one of these 4 symptoms that alert the driver of required servicing.

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

3. Leaking brake fluid

Brake fluid leaks from the master cylinder or unsecured reservoirs on the cylinder holding the fluid lower critical brake fluid levels. The brake master cylinder needs adequate levels of fluid to exert the right amount of hydraulic pressure to slow down the car. You’ll need to have the brake master cylinder replaced in this situation. If left unresolved, your ability to slow down the car will be impaired.

4. 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. Such issues may also ignite a Brake Warning Light too.

The brake master cylinder is essentially the heart of the braking system and vital to reliable brake operation. It is an important component of 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 to determine if it the car needs a brake master cylinder replacement.


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Johnny

33 years of experience
264 reviews
Johnny
33 years of experience
Toyota RAV4 L4-2.4L - Brake System Inspection - Sacramento, California
Johnny arrived early which was great, he performed the inspection in less than half an hour, and gave us a complete quote for all items needing attention, including the brakes as our main concern. Johnny is fast and efficient so I scheduled the work done by him.
Ford Escape - Brake System Inspection - Sacramento, California
The convenience is worth the cost. I was also tired of the dealership not really caring about my old car. Last couple of times I had to wait well over an hour to get my car after the dealership said "It's ready!". They also wouldn't fix the things I asked saying they didn't have time and I need to come back.

Jay

37 years of experience
947 reviews
Jay
37 years of experience
Chevrolet C10 Pickup V8-5.4L - Brake System Inspection - Moreno Valley, California
Knowledgeable, Professional, Friendly, and PATIENT! Sickeningly HONEST, as I tried to ply him with cash, alcohol, outside work, and wild dancing girls - although I wouldn't have "ratted him out" if he HAD accepted. A guy like this needs a "bigger cut" than what you are paying him ... because loyalty like his is hard to find these days! THANKS!
Volkswagen Jetta - Brake System Inspection - Moreno Valley, California
As usual, Mr. Jay provides efficient and professional quality of work. I would highly recommend him to any customer searching for a good mechanic.

Christopher

10 years of experience
114 reviews
Christopher
10 years of experience
Ford Explorer V6-3.5L - Brake System Inspection - Katy, Texas
Christopher was very knowledgeable and was able to address our concerns. We would trust him with future service needs.

Jesse

16 years of experience
61 reviews
Jesse
16 years of experience
Nissan Frontier V6-3.3L - Brake System Inspection - Flagler Beach, Florida
Jesse took the time to explain everything that was going to be done and why and then proceeded to repair my truck not only professionally but quickly. As a disabled Veteran and no longer able to perform work that was needed to be done it is nice to know a mechanic such as Jesse will take the time to explain all the various issues and what needs to be done before a blanket you need everything. After Jesse went thru everything I felt comfortable that all work was required and needed. 8 can safely say I will use yourmechanoc .com again and hope I can request Jess

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