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GENERAL DESCRIPTION
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The vehicle is equipped with a four wheel, vacuum
assisted,
hydraulic disc brake system. The disc
brakes are applied with separate front and rear
hydraulic circuits. The hydraulic pressure for these
circuits originates at a tandem master cylinder
which is operated with push rods. Brake application
is assisted with the aid of a
mechanical
/vacuum
power servo unit which is activated by brake pedal
application. The park brake mechanically operates
the rear brakes only.
Each wheel assembly is equipped with a fixed
caliper containing two opposing pistons (attached
to knuckle or carrier), a brake disc (positioned over
the hub and wheel studs) and a set of brake pads.
In addition to the service brake calipers and pads,
the rear brakes are equipped with independent and
separate park brake caliper and pad assemblies. The
park brake calipers and pads are operated with the
park brake lever inside the driver's compartment by
means of two (2) separate cables to provide park
and emergency braking of the rear discs. The park
brake caliper and pad assemblies are secured to the
rear service brake calipers. The park brake caliper
and pad assemblies are self-adjusting by means of a
spring loaded racheting pawl incorporated within
the caliper apply lever.
The tandem master cylinder consists of two (2)
independent cylinders in a single casting. Should
one cylinder or system
fail,
the other system will
remain operational. Each hydraulic system (front
and rear) has
a
separate brake fluid supply well in the
brake fluid reservoir which is mounted to the top of
the master cylinder. The brake fluid reservoir is
equipped with a float actuated, low fluid warning
indicator. However, this system is not equipped
with a low pressure indicator, a metering valve,
proportioning valve or a combination of these
valves.
The power assist from the brake servo unit is
developed by engine vacuum. Engine vacuum,
obtained from an intake manifold fitting, is applied
to both sides of a diaphragm inside the servo unit.
Depressing the brake pedal will allow atmospheric
pressure to enter one side of the diaphragm. This
difference in pressure develops the power assist
used in applying the brake systems. The servo unit
is located between the brake pedal and master
cylinder. The apply pressure is transferred through
two (2) in-line push rods. Should a vacuum failure
occur, the two (2) push rods will act as a single rod
and the brakes will continue to operate in the
unassisted,
conventional manner; however,
additional brake pedal effort will be required. A
vacuum check valve is used in the supply line where
it connects to the servo unit. This check valve
prevents vacuum loss from the servo unit after the
engine stops running and provides enough vacuum
reserve for emergency brake application. (Fig.
1)
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