How The Hydraulic System Works; Daily Brake Performance Test; Wheel Brake; Brake System Inspection - Ezgo WorkHorse ST 480 Technician's Repair And Service Manual

BRAKES
Read all of Section B and this section before attempting any procedure. Pay particular attention to all Notes, Cautions and Warnings
GENERAL

How The Hydraulic System Works

A hydraulic system actuates the rear brakes. The system
transmits the power required to activate the friction sur-
faces (brake shoes) of the braking system from the pedal
to the individual brake units at each wheel.
The hydraulic system operates as follows:
When at rest, the entire system is full of brake fluid. Upon
application of the brake pedal, fluid trapped in front of the
master cylinder piston is forced through the lines to the
wheel cylinders. Here, it forces the pistons outwards
against the brake shoes which in turn contact the brake
drum. Upon release of the brake pedal, a spring located
inside the master cylinder immediately returns the piston
to the normal position. The brake shoe return springs
retract the brake shoes and wheel cylinders which
returns the brake fluid to its original position within the
master cylinder.

Wheel Brake

The 160 x 30mm hydraulic brake is a leading-trailing
design. The shoes are held to the backing plate by hold-
down springs, pins, and spring retainers. The shoes are
fitted to the anchor at the bottom and secured by a lower
shoe to shoe spring. At the top, the shoe web rests on
the wheel cylinder piston. The shoes are held to the
wheel cylinder pistons by the upper shoe to shoe spring.
The wheel cylinders are of the double piston design, per-
mitting even distribution of force to each shoe. There are
no links. Shoes rest directly on the piston ends. Wheel
cylinders incorporate external boots.
Brake adjustment is automatic. Adjustment takes place, if
needed, whenever the brakes are applied, whether dur-
ing a forward or reverse stop or when the vehicle is sta-
tionary. Upon any brake application, the shoes move
outward contacting the drum. As the shoes move out-
ward, the automatic adjuster levers (attached to each
shoe by a pin) follow the shoe movement. The automatic
adjuster pin is smaller than the slot in the brake shoe
web; therefore, when the brakes are released, the shoes
are allowed to return slightly, providing brake shoe to
drum running clearance.
The rear brake includes a parking feature consisting of a
lever and strut. The lever is applied by a cable attached
to the parking brake lever (hand operated). The parking
brake is used to retain the vehicle when stationary. It may
also be used as an emergency brake in the event of
hydraulic system failure.
Page D-2
MAINTENANCE

Daily Brake Performance Test

must be performed as indicated in the Periodic Service Sched-
ule in Section A of this manual. It is important that a Daily
Brake Performance Test be performed and the entire brake
system be serviced in accordance with the Periodic Ser-
vice Schedule.
The brake system must be bled whenever any part of the
brake system has been replaced.
Depress brake pedal. The pedal should have some free
play and then become hard. A brake pedal that has no
free travel, excessive free travel or a spongy feel indi-
cates a brake inspection is required. A brake pedal that
falls after it is applied indicates a leak in the master or
wheel cylinders. Check brake fluid level. Adjust brakes if
required and inspect system for fluid leaks.

Brake System Inspection

Brake failure usually occurs as either a gradual decrease
in braking effect from the shoe material being worn away,
a loss of braking at one wheel or a sudden and complete
failure with no brakes working except the parking brake.
Should the brakes at one wheel become ineffective while
the brakes at the other wheel functions properly, remove
the wheel and drum. See 'BRAKE DRUM REMOVAL
AND INSTALLATION' on page D-5. Inspect the brake for
evidence of a leaking or inoperative wheel cylinder
assembly.
If the brake shoes should become wet with hydraulic fluid,
remove the brake drum and wipe the brake shoes and drum
until they are dry.
Complete brake failure usually indicates a loss of hydrau-
lic fluid pressure.
The hydraulic system may be checked for leaks by
applying pressure to the pedal gradually and steadily. If
the pedal sinks very slowly to the floor, the system has a
leak. This is not to be confused with a springy or spongy
feel due to the compression of air within the lines.
Check for leaks along all lines and at brake assembly. If
no external leaks are apparent, the problem is inside the
master cylinder.
Repair and Service Manual
To assure correct braking performance, all peri-
odic maintenance, inspections and procedures
Care should be taken to prevent brake fluid
from coming into contact with the brake shoes.
Do not allow brake fluid to contact
painted surfaces. Wipe off immediately.