5 Symptoms of a Bad Brake Master Cylinder and Replacement Cost


When you step on the brake pedal in a vehicle to slow it down, its braking system uses a brake master cylinder to convert the pressure you place on the pedal into hydraulic pressure. The conversion of the pressure takes place because the brake master cylinder transfers brake fluid to the braking circuit as you step on the brake pedal. The brake master cylinder will do this no matter if your vehicle is using disc brakes or drum brakes. There is no way any braking system could exist without a brake master cylinder.

5 Symptoms of a Bad Brake Master Cylinder

Once the brake master cylinder starts to go bad, there will be certain noticeable symptoms that will arise. Below are the top 5 symptoms of a bad brake master cylinder that you will surely notice.

  1. Warning Light – The first symptom that is the easiest to notice is when the Brake Warning Light illuminates on the dashboard. This indicates that there is some kind of problem with the braking system, so it might not necessarily mean that the brake master cylinder is at fault. But if the braking system sensors detect the brake fluid pressure is dropping, it will likely be due to a bad brake master cylinder. This will result in the warning light coming on.
  2. Leaky Brake Fluid – The brake master cylinder needs a certain level of braking fluid to create the hydraulic pressure necessary for slowing down the vehicle. If the brake master cylinder is leaking braking fluid or if there are unsecured reservoirs on the cylinder which are holding the fluid, then you will have a low brake fluid level for sure. This will impair your ability to slow down the vehicle. You would need to replace the brake master cylinder in this situation.
  3. Spongy Brake Pedal – When the brake pedal starts to feel spongy as you place pressure on it with your foot, this will automatically be a sign that your brake master cylinder is having issues. The cylinder contains rubber seals which keep the brake fluid inside of it. If these rubber seals were to get worn out or damaged, then there’d be an internal brake fluid leak. The result of this would be a spongy feeling in the brake pedal.
  4. Contaminated Brake Fluid – Another problem that could happen as a result of worn out rubber seals is contamination in the brake fluid. The seals not only help keep the brake fluid from coming out, they also prevent dirt and debris from mixing with the brake fluid. If this were to happen, the brake pressure would not be as strong as you step on the brake pedal. You’d probably end up pressing down harder on the pedal just to get the vehicle to slow down like normal.
  5. Sinking Brake Pedal – Following all these other symptoms, you will start noticing the brake pedal not returning to the top after you’ve removed your foot from it. Instead, it will slowly sink to the floor. This could become a real driving hazard, so you’ll want to fix the brake master cylinder right away at this point.

Read also: 5 Symptoms of a Bad CV Joint and Replacement Cost

The Average Replacement Cost

If you have a brake master cylinder that goes bad, the average cost to replace the cylinder will be between $320 and $500. The cost of the part itself will only be around $100 to $210. But the biggest expense of the replacement job will be in the labor costs, which are around $230 to $300. If you were to be knowledgeable in vehicles and braking systems, then you would be able to save a fortune on the labor costs by doing it yourself. However, it is a job that requires you to be a professional mechanic or else you may mess something up.


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