How Do I Determine if a Master Cylinder Is Bad?

Written by jen davis
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How Do I Determine if a Master Cylinder Is Bad?
A bad master cylinder can cause brake failure. (Jupiterimages/ Images)

Your vehicle's master cylinder controls the fluid in your braking system. If your master cylinder is damaged or malfunctions, your brake system will not have the fluid it needs to maintain proper pressure. Consequently, your brakes may become soft or even stop working altogether, depending on the severity of the problem. Fortunately, there are several different issues you can easily monitor that will help you determine whether your master cylinder has gone bad.

Skill level:


  1. 1

    Check your brake fluid. The master cylinder and the brake fluid reservoir are connected and if your fluid keeps running low, your master cylinder may be leaking. If your fluid level stays steady, but your brakes have no pressure, your master cylinder may not be functioning properly.

  2. 2

    Look for leaks. Inspect the area under the hood of your car around the master cylinder for leaks, as well as the ground directly underneath. You will also want to check your car's brake lines and wheel cylinders for leaks, as leaks in other parts of your braking system can be the reason why your master cylinder keeps losing fluid. If you can see your master cylinder has been leaking, you should replace it immediately.

  3. 3

    Press down on your brake pedal. If it is soft, goes down to the floor or otherwise does not seem to have its normal pressure, your master cylinder may not be working properly.

  4. 4

    Look for error code lights. If your brake light is coming on, a bad or malfunctioning master cylinder may be triggering it.

  5. 5

    Have your car examined by a mechanic. A mechanic will be able to scan the car's error codes and tell you if the master cylinder is causing the problem. Your mechanic may also be able to identify other problems in your brakes and determine whether the problem is truly being caused by the master cylinder. If your master cylinder is the problem, you should have your mechanic replace it immediately.

Tips and warnings

  • Do not drive your vehicle will malfunctioning brakes or if you suspect you may be having braking problems. This can cause serious accidents, injuries or death.

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