Replacing the master cylinder on a 1988 Honda Civic is not complicated, as it is located in the engine compartment and mounted to the power booster. The master cylinder distributes brake fluid to the brakes when the pedal is pressed. The brake system is a hydraulic system that uses the fluid to activate the calipers. A bad master cylinder will lose brake fluid and cause air to get into the system, making the car hard to stop.
Tools Used: Socket wrench, Socket set, New o-rings, New master cylinder, Line wrench set, Brake fluid, Plastic tube, Drain pan
Change Brake Master Cylinder
Replacing the Master Cylinder
Open the hood for access to the engine compartment. Locate the master cylinder at the back of the engine compartment on the driver's side.
Disconnect the two brake lines going into the master cylinder with a line wrench. Ensure you have a pan in place to catch the brake fluid leaking out.
Unbolt the two bolts at the back of the cylinder with a socket wrench. These two bolts keep it connected to the power booster. Pull the master cylinder away from the power booster and out of the engine compartment. Place the old cylinder in a drain pan to prevent the brake fluid from making a mess.
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-ring will be located in the fittings.
Screw the brake lines onto the master cylinder by hand. Tighten them with a line wrench to ensure the lines are secure.
Open the reservoir by hand. Fill to the designated level with brake fluid. The level will be indicated on the side of the master cylinder. Tighten the cap back on to the master cylinder.
Bleeding the Brakes
Instruct a partner to sit in the driver's seat. Instruct him to start the car.
Locate the bleeder valve on the rear left wheel of the car. The bleeder valve will be located on the top of the brake assembly.
Insert a plastic tube onto the top of the bleeder valve. Ensure the other end of the tube is in a drain pan. This will be used to catch any additional brake fluid.
Loosen the bleeder valve with a 7/16" wrench. Turn it counterclockwise one full turn to loosen it, then close the valve.
Instruct the assistant to press the brake pedal repeatedly several times and then hold the pedal down. Let the assistant know that the pedal may sink toward the floor, but he must keep pressure on the pedal. Open the valve about one quarter turn, then tighten the valve as brake fluid stops coming out of the line. When the valve is closed, tell the assistant to release the pedal. Repeat this process several times until air bubbles no longer flow out with the brake fluid. Make sure the assistant knows not to release the pedal until told.
Monitor the level of brake fluid in the master cylinder throughout the bleeding process, and refill as needed to keep it from getting more than half empty. Do not fill past the line on the side of the reservoir.
Repeat the bleeding procedure on the three remaining wheels. Bleed the driver side rear wheel, passenger side front wheel and the driver side wheel.
Tips & Warnings
Do not let the master cylinder go dry in the process of bleeding. This will let air in to the brake lines and the process of bleeding will need to be done again.
Do not allow the pedal to be released while the bleeder valve is open. This will suck air back into the lines.
Use extreme caution when working underneath the car. Ensure the parking brake is set and the car is on a flat, level surface.
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