TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 88 of 481
TM 9-2320-272-10
1-71
1-20. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
I
TRANSMISSION VENT
–
Vents internal air pressure build-up due to
internal heat.
A
SPRING BRAKE RELEASE CONTROL VALVE
–
This valve functions as
an override when a failure in the air supply system (causing spring brakes to
engage) occurs. When valve is manually pushed in, emergency air is supplied
to the spring brake chambers. This releases the spring brakes, allowing
vehicle movement.
J
SPRING PARKING BRAKE VALVE
– Vents air pressure from air and
doublecheck valves #3 and #4.
B
PEDAL VALVE
– Vents primary or secondary signal air pressure when
pedal is released.
D
LIMITING VALVE
– Vents signal air pressure going to front brake
chambers so rear brakes apply first.
E
STEP BOX QUICK-RELEASE VALVE
– Vents air pressure from spring
brake chambers when parking brake valve has been actuated.
F
REAR BRAKE CHAMBERS
– Vents ports on chambers to prevent air
pressure build-up.
H
AIR INTAKE STACK
–
Venting point for the vent system.
L
FUEL TANK VENTS
–
Vent fuel vapors to prevent partial vacuum from
stopping fuel flow.
C
FRONT BRAKE CHAMBER VENT
–
Vents air pressure inside chambers
when pedal valve is released.
K
TRANSFER CASE VENT
–
Vents internal air pressure build-up due to
internal heat.
G
RELAY VALVES
– Vents air pressure in rear brake chambers directly to
intake tube when brake pedal is released. Vents signal air pressure through
upper port in valve.
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