Understanding the Brake Master Cylinder

Deep in the engine compartment, you find the heart of the brake system, the master cylinder. The master cylinder is a hydraulic pump that supplies hydraulic fluid under pressure to each of the wheels. Anything affecting the braking system of a vehicle is of utmost importance to the safety of the passengers.

Maintaining the entire braking system will ensure that you and your passengers ride in the safest conditions. Wet, icy, or even average road conditions can be very dangerous when the brakes aren’t functioning to their highest ability.

If you suspect any problems with your brakes, get a professional to check it out immediately. With the brake system, many times when the symptoms show up, it is already too late. Preventative maintenance will eliminate the need for more expensive repairs.

The master cylinder and brake booster are replaced, removed and repaired as a single unit. If you have decided to do the installation yourself, there is one important item you should note. Often the master cylinder is filled with brake fluid before it is installed. Brake fluid is very damaging to paint. Be sure to appropriately protect your car’s paint before filling the master cylinder anywhere near it.

Replacing this assembly requires a great deal of care, a significant amount of time and experience generally not afforded to the average shade tree mechanic. In addition, the disassembly required to reach the parts is extensive requiring a large number of rather specialized and generally expensive tools making this repair costly, complicated and not likely cost effective to the average person. Completing this repair at a dealer will run an average of $350. A much more cost-effective option would be buying the tools needed to do the repair yourself.

Brake System Master Cylinder Diagram

When the master cylinder seal fails, it generally creates a brake fluid leak at the junction of the master cylinder and the brake booster.

Since the brake master cylinder and brake boosters are removed as one assembly, most mechanics recommend replacing a leaky master cylinder instead of repairing it. The cost is not much more and the new master cylinder will provide all new parts including the switch light.

Accessing the master cylinder requires a tremendous amount of disassembly (including the dash cover, carpeting, footplate, etc). For this reason, we recommended that you seek the advice of a professional mechanic rather than attempting this repair yourself. This is especially true if you have limited access to professional equipment.

In addition to the professional equipment and time saved by allowing a professional to do this repair, you should expect to receive a warranty with this repair. Be sure to ask about warranty information and save the associated paperwork.

How Brake Master Cylinders Work

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