224
Brakes
Do not release the parking brake or at-
tempt to move the vehicle until brake air
pressure in both circuits is at least 100
psi (690 kPa). Failure to follow this pro-
cedure may lead to uncontrolled vehicle
movement and cause severe personal in-
jury or death.
Never release or drive a truck that has a
brake discrepancy — no matter how mi-
nor — until it has been repaired or
corrected. Failure to repair brake dis-
crepancies can result in compromised
brake efficiency and may lead to loss of
control of the vehicle resulting in severe
personal injury or death.
General
All Volvo vehicles are designed to meet or
exceed all applicable federal brake stan-
dards and regulations. They use a dual
circuit, compressed air system. It consists
of two independent brake systems that use
a single set of brake controls. Each circuit
is supplied by its own compressed air tank.
Both air tanks receive compressed air from
the same supply tank (wet tank) and are
charged with equal pressure. The two cir-
cuits are interconnected for the parking
brake system.
Air pressures in the two circuits are moni-
tored by two pressure gauges on the right
side of the instrument cluster. The primary
(rear) brake circuit gauge is marked with an
“R” within a symbol and the secondary
(front) brake circuit gauge is marked with
an “F” within a symbol. The two pointers
should register equal or nearly equal pres-
sure. By observing the gauge pointers, the
operator is forewarned in the event of a
pressure drop in either or both of the cir-
cuits. See page 85 for more information.
Before operating the vehicle, check the air
gauges which indicate air pressure. They
should not register less than 105 psi
(725 kPa). Maximum pressure at any time
should not exceed 150 psi (1035 kPa).
W3003637
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