How to Install a Master Brake Cylinder

A vehicle's master cylinder converts the motion of the brake pedal into hydraulic power, which is then transmitted to the brakes. As a safety feature, the cylinder is actually two cylinders; one acting on the front right and rear left brakes, and the other acting on the other two brakes. In this way, a failure of one part of the master cylinder will not result in a complete brake failure. Problems can develop in the master cylinder, however, that will require the unit to be replaced. A low brake pedal is usually a sign that drivers need to replace the master cylinder.

Instructions

1

Park the vehicle on level ground. Open the hood and locate the master cylinder, which will be near the rear wall of the engine compartment on the driver's side, roughly in line with the top of the brake pedal. The master cylinder will be attached to the front of the brake vacuum booster. The brake fluid reservoir is located just above the master cylinder, and the four brake lines connect to the lower part of the master cylinder.

2

Remove the cap of the brake fluid reservoir. Use the turkey baster to remove as much of the brake fluid from the reservoir as possible.

3

Disconnect the brake-fluid-reservoir-level sensor, if present, by pulling the wiring connector off of the sensor terminal. Place a plastic container under the master cylinder to catch any spills and drips. Disconnect the brake lines by removing the flare-nuts and pulling the lines clear of the cylinder. Be careful not to strip the flare-nuts or damage the brake lines.

4

Remove the two nuts that secure the master cylinder assembly to the brake vacuum booster. Pull the master cylinder and brake fluid reservoir assembly off the studs that extend from the booster.

5

Slip the new master cylinder and brake-fluid-reservoir assembly onto the booster studs and secure with the nuts. Reattach the brake lines to the master cylinder and the wiring for the reservoir-level sensor.

6

Fill the reservoir with brake fluid. The proper type of brake fluid is usually written on fluid reservoir cap, or in the vehicle owner's manual. Locate the brake bleeder connections on each of the four brakes. Attach one end of a length of clear tubing to each bleeder connection, and put the other end in a plastic container set securely on the ground. Open the bleeder connections on all four wheels until brake fluid begins to drip out of the bleeder connection. On some vehicles. you will have to jack the vehicle up and remove the wheels to access the brake-bleeder connections.

7

Have and assistant start the engine and gently press the brake pedal down. Examine the brake fluid as it comes out of the four brake-bleeder connections, looking for air bubbles trapped in the fluid. Close the bleeder connections. Have the assistant release the brake pedal. Refill the brake fluid reservoir with new fluid, and repeat the procedure until no air bubbles are visible at the bleeder connections.

8

Close the brake bleeder connections and remove the plastic tubing. Fill the brake fluid reservoir to the full mark, and replace the cap. Test the brake operation before driving normally. Dispose of all used brake fluid in accordance with local regulations.