How to Replace Car Brake Master Cylinder
The brake master cylinder is the manual hydraulic pressure part of the brake system. The brake master holds hydraulic brake fluid that is used to actuate the brake system. Brake fluid flows through brake system components and then to the front brake caliper under pressure to slow the vehicle. When a master cylinder fails you may experience alow brake pedal, the master cylinder is divide into two separate sections, the primary and secondary pressure systems. This system was created inside the master cylinder for safety; if one half of the brake system fails you will still have the remaining half to help slow the vehicle. Note: You must know how tobleed a hydraulic brake system before you can service or change a master cylinder.
Single Car Brake Master Cylinder (early cars for front and rear brakes)
Step 1 - Identify Brake Master Cylinder and Reservoir
Identify brake master cylinder components,brake fluid cap, brake master cylinder, fluid lines, and brake fluid level sensor. Inspect for any brake fluid leakage around the master cylinder and check for proper fluid level regularly. If leakage is present replace master cylinder immediately.
Step 2 - Removing Brake Fluid
Remove brake fluid reservoir cap and insert brake fluid removal tool, remove as much brake fluid as possible. Then refill and reinstall brake fluid reservoir cap.
Step 3 - Removing the Brake Fluid Level Sensor Connector
Remove the electrical connector to the fluid level sensor. Most connectors have safety clips that need to be released before they will disconnect.
Step 4 - Removing Brake Fluid Lines
Install a line wrench firmly on the brake fluid lines departing from the master cylinder. A line wrench is a special wrench that holds five points of the fitting as opposed to two points like a normal wrench, which gives this special wrench more power without damaging the fitting than a normal wrench. Apply force to the wrench in a counter clockwise motion to loosen and remove fitting and line in the master cylinder. Repeat operation until all fluid lines are removed. Note: brake fluid will leak from brake lines when removed.
Step 5 - Removing Master Cylinder Mounting Bolts
Insert socket wrench onto master cylinder mounting bolts. After mounting bolts are removed, lift the master cylinder off the mounting studs and out of the vehicle.
Step 6 - Reinstall and Bleed Master Cylinder System
Reinstall master cylinder, tighten master cylinder mounting bolts and reconnect the fluid lines and fluid level sensor. Refill the master cylinder with new fluid most carsuse DOT3 or DOT4 but you should consult the cap on the master cylinder or your owner's manual orrepair manual. Once the master cylinder is full loosen all four brake fluid bleeder screws on the brake caliper or wheel cylinder. Next, press the brake pedal down completely, while holding the brake pedal down have a helper close all four brake bleeder screws. Now allow the brake pedal to return to normal position slowly, this will draw new fluid into the master cylinder body. Continue this procedure until the brake fluid is clean with no air bubbles out of each bleeder, close all bleeders and refill the master cylinder with brake fluid to the proper level.
Master cylinder fails illuminating the brake warning light
Master cylinder leaks fluid illuminating the brake warning light
Master Cylinder actuator rod is adjusted out to far not letting the brake master plunger not to return all the way creating residual brake pressure causing the brakes to drag
Dual Car Brake Master Cylinder (Later cars split for front and rear brakes)