Truck must be on level ground and wheels
must be chocked before parking brake is
released. Otherwise, truck may roll and
cause injury to personnel.
Wear safety goggles when performing leakage
tests on valves. Failure to do so may
result in serious eye injury due to high
If air lines are under high pressure when
they are disconnected, they can whip around
and cause injury to personnel. Caution
should be exercised when loosening or
disconnecting air line fittings.
(1) Start engine and build pressure
to 125 ±4 psi (861 ±28 kPa)
(2) Turn OFF ENGINE switch.
(3) Disconnect air line 2022 from right
air chamber on Axle No. 3.
(4) Connect a 0 to 160 psi (0 to 1103 kPa)
gage to air line 2022.
(5) Release and apply PARKING BRAKE.
(a) If there are 125 ±4 psi
(861 ±28 kPa) present at air line
2022, perform Steps (6) and (7)
below and replace relay spring
valve No. 1 (Para 12-16).
(b) If there are not 125 ±4 psi
(861 ±28 kPa) at air line 2022,
relay spring valve No.1 is OK.
(6) Apply PARKING BRAKE.
(7) Remove gage and connect air hose
2022 to air chamber.
RELAY SPRING VALVE NO. 1 TEST
(1) Listen to air chamber while
assistant releases and applies
(a) If assistant cannot hear air
chamber operate, or the brake
shoe does not move when
parking brake control is
pushed and pulled, perform
Step (2) below and replace air
chamber (Para 12-10).
(b) If air chamber operates
correctly, air chamber is OK.
(2) Release PARKING BRAKE.