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How Do I Repair My Car? /
How Do I Change
My Master Cylinder?
How Do I Replace My Brake Master Cylinder?
WARNING! Always have the vehicle under inspection
on level ground, in park with the emergency brake on. Always wear protective eyewear,
gloves and necessary clothing before inspection or work begins. Never crank an engine
over when anyone is near the battery or engine. Always have an operational fire extinguisher
close by, obey all first aid instructions in the event of an injury. Never stand
in front or behind a vehicle when cranked over or running. When engine is cranked
over keep hands and clothing away from rotating components. Never move a car without
proper brake pedal operation.
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 a low 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 to bleed
a hydraulic brake system before you can service or change a master cylinder.
READ COMPLETELY BEFORE STARTING!
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 cars use DOT3 or DOT4 but you should consult the cap on the master cylinder
or your owner's 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.
CAUTION: DO NOT DRIVE OR MOVE A VEHICLE UNTIL NORMAL BRAKE PEDAL OPERATION IS PRESENT!
Common Problems:
1. Master cylinder fails illuminating the brake warning light.
2. Master cylinder leaks fluid illuminating the brake warning light.
3. 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.
How Do I Repair
My Car?
/ How Do I Change
My Master Cylinder?
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