Symptoms of a Bad or Failing Brake Master Cylinder

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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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Rating Summary
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Pierre

8 years of experience
24 reviews
Pierre
8 years of experience
BMW 740iL - Brake System Inspection - Weymouth, Massachusetts
Absolutely Grateful for the knowledge he had, the many small things he pointed out to me, that ment a lot. Looking forward to making sure the gets exactly what it needs, for me to enjoy it! Thanks Again! :Mark C. Pierce 98 BMW 740 il

Helder

31 years of experience
28 reviews
Helder
31 years of experience
Dodge Durango - Brake System Inspection - Attleboro, Massachusetts
Very nice guy, he’s worked on my car twice so far and he’s been great. On time, and very professional

Mazyar

7 years of experience
171 reviews
Mazyar
7 years of experience
Pontiac Montana - Brake System Inspection - Atlanta, Georgia
Mark was personable. Very professional. I was so impressed that I asked if he could come back to do the follow up when I was ready.

Joel

20 years of experience
766 reviews
Joel
20 years of experience
Infiniti G35 - Brake System Inspection - Jacksonville Beach, Florida
Joel was great. Honest fast and professional. He is the automobile maintenance version of the trusted family doctor, attorney etc. Good to have a QB to save time and $pin job at dealership etc!

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