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.


Next Step

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Jesse

17 years of experience
127 reviews
Jesse
17 years of experience
Jaguar S-Type V8-4.2L - Brake System Inspection - Palm Coast, Florida
Jesse showed up for the appointment timely and ready to work. He was polite and professional and competent. He took sufficient time to inspect the vehicle and explained in layman's terms any problems and whatever corrective work that might be required. I highly recommend Jesse and hope to have him service my vehicles again in the future if needed.
Ford Escape - Brake System Inspection - Daytona Beach, Florida
Jesse arrived on time after sending notice 15 mins prior. A true professional Jesse got right down to business. He started his inspection work right away and did a thorough professional job and determined the solution to his findings. I am very pleased. He is a true expert mechanic.

Johnny

34 years of experience
392 reviews
Johnny
34 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.

Luis

30 years of experience
119 reviews
Luis
30 years of experience
Honda Accord V6-3.0L - Brake System Inspection - Northbrook, Illinois
He's excellent. On Time, honest and all repairs done quickly and correctly. Book him if he's available!

Christopher

16 years of experience
246 reviews
Christopher
16 years of experience
Nissan Sentra L4-2.0L - Brake System Inspection - Charlotte, North Carolina
Very informative and made sure to clarify on what he spoke on so that I understood what was happening with my car

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