Master Brake Cylinder ?

[WB9MCW]

Brake Hose May Cause Low Pedal

How to diagnose a sinking, low or spongy brake pedal.

1. Begin by isolating the master cylinder. Remove the lines from the
master cylinder and insert blocking plugs into the ports. Press on
the brake pedal. If the pedal is firm and hard, the master cylinder
is good. If the pedal still drops, either air is in the unit or it is
bypassing internally. Bleed the unit or replace as necessary.
Reconnect and bleed the system.

2. With a properly bled master cylinder test the brake hoses. Using
a proper tool, carefully pinch off all the rubber brake hoses as
close to the master cylinder as possible. Release one brake hose
at a time. Press the brake pedal. If the brake pedal is firm and
hard, move to the next circuit. Repeat until the circuit containing
the defective component is located (the brake pedal will be soft
or sinking). Replace defective components as necessary.



3. Flush the system thoroughly with fresh brake fluid from a sealed
container according to the manufacturer’s service procedures.