TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 1032 of 1313
INSUFFICIENT BRAKES (VEHICLE STOPPING DISTANCE TOO LONG, NO APPARENT AIR SYSTEM
FAILURE WITH GAUGES AT NORMAL OPERATING PRESSURE, WARNING BUZZER NOT SOUNDING) -
Continued
d.
Disconnect air line from elbow at primary relay valve delivery port (Volume 3, WP
0458). Refer to point
to point schematics.
e.
Remove elbow from primary relay valve delivery port.
f.
Connect pressure gauge to disconnected relay valve delivery port.
g.
Assistant starts engine and runs to build air supply to normal operating pressure.
h.
Assistant fully applies and holds service brakes.
i.
Monitor air pressure on pressure gauge.
j.
Pressure gauge should read 90 to 130 psi.
CONDITION/INDICATION
IS PROPER AIR PRESSURE AT PRIMARY RELAY VALVE?
DECISION
NO - Go to Step (25).
YES - Replace damaged air lines from primary relay valve to rear brake chambers (Volume 5, WP
0805). Go
to Step (30) to verify problem is solved.
TM 9-2320-272-23-1
0120
0120-43
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