TRUCK SERVICE MANUAL
The hydraulic system used to actuate the brake
mechanism consists of a compensating type master cylinder,
in which the hydraulic pressure is originated; individual wheel
cylinders, in which the hydraulic pressure is applied, which
serve to actuate the brake shoes against the brake drum of
each wheel; and the "line" consisting of steel tubing, flexible
hose, brackets and unions, interconnecting the master
cylinder and wheel cylinders. The master cylinder and wheel
cylinders are fitted with pistons, all of which are provided with
cup packings, which act as a seal to maintain pressure and
prevent loss of brake fluid.
Depressing the brake pedal moves the piston within
the master cylinder, thus displacing the brake fluid from the
master cylinder through its outlet orifices, tubing and flexible
hose connection into the wheel cylinders. The brake fluid,
being non-compressible, enters each of the wheel cylinders,
causing the cylinder pistons to move outward and actuate the
brake shoes. As pressure on the pedal is increased, greater
hydraulic pressure is built up within the wheel cylinders and,
consequently, greater force is exerted against the shoes.
When the pressure on the pedal is released, the
brake shoe retracting springs return the brake shoes to their
normal or released position. The return movement of the
brake shoes, in turn, causes movement of the wheel cylinder
pistons toward their released position, thus forcing the fluid
back through the tubing into the master cylinder.
The brake system should be checked periodically for
evidence of needed repairs.
It is difficult to determine an exact maintenance
interval (time or mileage) since vehicles will be used in wide
varieties of operational applications and conditions.
Brake adjustment should be checked every 3,000 km
(2,000 miles). Brake lining should be inspected every 19,000
km (12,000 miles) or every 12 months which ever occurs first.
Before starting to check out the brake system itself,
the following related components on the vehicle should be
examined and serviced if found defective.
The following procedure is given as an aid in
checking out the brake system.
Pedal return should be unrestricted when pedal is
fully released (see BRAKE PEDAL ADJUSTMENTS
in Chapter III).
Excessive side movement indicates worn pedal
There should be ample clearance between pedal and
toe board when pedal is fully depressed (brakes
Pedal height should be corrected (see BRAKE
PEDAL ADJUSTMENTS in Chapter III).
To check power cylinder for correct operation, refer
to the respective "Power Cylinder" section of this Service
Fluid level should be 6.4 to 12.7 mm (1/4 to 1/2")
from top of reservoir.
Master cylinder vent must be clear and unrestricted.
Check for external leaks at hydraulic line connections
or at push rod end.
CTS-2055S Chapter 1 Page 3
PRINTED IN UNITED STATES OF AMERICA