How to Replace the Master Cylinder on a 1986 Chevrolet Caprice

A 1986 Chevrolet Caprice Station Wagon uses a hydraulic system for braking. The system starts at the master cylinder, which is used to send fluid to each of the calipers when the brake pedal is pressed. When the master cylinder is faulty, air will get into the lines and cause the car to not stop. Replacing the master cylinder includes bleeding the brake system to evacuate all the air in the lines.

Tools Used: Line wrench, Socket wrench, Socket set, New master cylinder, Drain pan, DOT 3 brake fluid, Rubber or plastic tube, Assistant

Replace Master Cylinder

Replacing the Master Cylinder

Open the hood for access to the master cylinder. The master cylinder is located on the firewall, mounted to the power booster.

Unscrew the brake lines with a line wrench. Pull them out and away from the master cylinder.

Unbolt the two bolts holding the master cylinder to the power booster. Pull the master cylinder out from under the hood, and place it in a drain pan to drain the brake fluid out of it.

Bolt the new master cylinder to the power booster with a socket wrench. Ensure both bolts are tight.

Replace the o-rings in the brake lines. The o-rings are included with the master cylinder.

Position the brake lines to the master cylinder. Hand tighten the lines to start them, then tighten with a line wrench to ensure the lines do not leak.

Fill the master cylinder with DOT 3 brake fluid. Place the cap back on. Do not overfill the master cylinder--refer to the fill line designated on the side.

Bleeding the Brakes

Locate the bleeder valve on the back passenger side wheel. (The valve is a small cylindrical shaped valve that sticks out of the top of the brake assembly.) Place a rubber or plastic tube on the bleeder valve, and the other end of the tube in a drain pan.

Have an assistant sit in the driver seat and start the car. They will be required to pump the brake pedal as you loosen the bleeder valve.

Open the bleeder valve with a 7/16-inch wrench. Turn the wrench counterclockwise one full turn. Have your assistant pump the brake pedal. Instruct them to stop once clear brake fluid flows out of the bleeder valve. Tighten the bleeder valve. Instruct the assistant to pump the brake pedal repeatedly to build pressure in the brake pedal. Repeat this step again to ensure all the air is out of the brake line.

Fill the master cylinder with brake fluid. Do not let the master cylinder go empty--this will cause air to get in the lines.

Repeat this process to bleed the remaining three wheels. Do not let the master cylinder run dry.

Tips & Warnings

Use only DOT 3 brake fluid for the master cylinder.

Do not let the brake fluid touch the paint on the car. The brake fluid is hazardous to the paint on the car.

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