Page K-22
Repair and Service Manual
B
BRAKES - FRONT DISC
Read all of Section B and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
SYSTEM DESCRIPTION
To assure correct braking performance, all periodic mainte-
nance, inspections and procedures must be performed as indi-
cated in the Periodic Service Schedule in Section ‘A’ of this
manual. The brake system must be bled whenever
any part of
the brake system
has been replaced.
A hydraulic system is used to actuate the front brakes.
The system transmits the power required to activate the
friction surfaces (pads) of the braking system from the
pedal to the individual disc brake hubs at each wheel.
The front hydraulic brake system is designed to operate
only after significant rear brake pressure has been
applied. This is accomplished by activating the master
cylinder after the brake pedal has reached the parking
brake latch position. The lower actuator pivot is con-
nected to the brake pedal by a linkage rod which rotates
to contact the upper actuator pivot. The upper actuator
pivot is connected to a clevis of the master cylinder
plunger. Movement of the plunger hydraulically activates
the caliper pistons forcing the brake pads against the
rotors. With the brake pedal released, the upper actuator
pivot and the plunger returns to the ‘at rest’ position.
With the master cylinder no longer applying hydraulic
pressure to the brake pistons, the piston seals retract
the pistons permitting the brake pads to float freely
against their guide pins while removing all pressure
against the rotors.
MASTER CYLINDER REPLACEMENT
During this process, it is likely that brake fluid will leak
from the master cylinder. Avoid allowing brake fluid to
contact the painted body components of the vehicle.
Wipe off immediately.
Removing the front shield may improve access (See
BODY).
To remove the master cylinder:
Remove the bolts securing the brake actuator assembly
housing cover and remove cover. The clevis pin joining
the brake cylinder clevis and the upper actuator pivot
must be removed by removing the cotter pin and dis-
carding. Remove clevis pin (Ref. Fig. 30).
Remove the braided brake line from the master cylinder
and allow brake fluid to drain into a container.
Do not
reuse old brake fluid.
Remove the two nuts, bolts and
washers securing the master cylinder to the brake actu-
ator assembly housing. Install new master cylinder, and
tighten nuts to 12 - 14 ft. lbs. (16.2 - 18.9 Nm) torque.
Install brake line to new master cylinder and tighten to
15 in. lbs. (1.6 Nm) torque.
Latch the brake pedal. Rotate and hold the upper actua-
tor pivot against the lower actuator pivot. (Rotate and
hold the upper actuator pivot such that the rectangular
stop tab contacts the lower actuator pivot stop tab.)
Adjust master cylinder clevis until the clevis pin passes
through the upper actuator pivot and the master cylinder
clevis. Tighten jam nut against master cylinder clevis.
Install a new cotter pin. Bleed hydraulic system.
Add clean fresh DOT 3 brake fluid into reservoir and
bleed system per ‘BLEEDING BRAKES’
Fig. 30 Master Cylinder Replacement.
BRAKE MASTER CYLINDER FLUID
Hydraulic brake systems must be totally flushed if the fluid
becomes contaminated with water, dirt or other corrosive
chemicals. To flush, bleed the entire system until all brake fluid
has been replaced with fresh DOT 3 standard automotive
brake fluid.
Check Brake Fluid
The brake fluid should be checked at regular intervals
(as specified in the Periodic Service Schedule) or imme-
diately if fluid leaks are found. The easiest way to check
fluid level is to clean the cap with a shop rag and remove
the cap. Check fluid level using a mechanics mirror and
a flashlight. Add fluid if the level has fallen below 1/4”
from the top of the reservoir and inspect for visible fluid
leaks.
NOTICE
Brake Actuator
Assembly Housing
Housing
Cover
Master Cylinder
Clevis pin
Cotter Pin
Clevis
Lower Actuator Pivot
Upper Actuator Pivot
NOTICE
Summary of Contents for EXPRESS L6 2012
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