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 60 of 481
TM 9-2320-272-10
1-43
1-18. POWER SYSTEM OPERATION (Contd)
SURGE TANK
– Filling point for cooling system. On M939A2 vehicles, a
float sensor monitors water level and illuminates a light on instrument panel.
COOLANT PRESSURE CAP
– Designed to depressurize cooling system and
to access cooling system for filling.
WATER MANIFOLD
– Collects coolant from cylinder heads and directs it to
the thermostat housing (M939/A1 series only).
SURGE TANK-TO-WATER MANIFOLD VENT
– Vents air trapped in
water manifold (M939/A1 series only).
SURGE TANK-TO-RADIATOR VENT
– Vents air in cooling system.
THERMOSTAT
– Shuts off coolant flow to radiator until temperature
reaches 175°F (79°C) on M939/A1 series vehicles, and 181°F (83°C) on
M939A2 series vehicles. Coolant is then directed to the radiator through the
radiator inlet hose.
RADIATOR INLET HOSE
– Directs coolant from water manifold to radiator
after thermostat has opened.
BYPASS TUBE
– Directs coolant back to transmission oil cooler where it is
then recirculated through the engine block until the thermostat opens.
RADIATOR SHROUD
– Concentrates air flow through the radiator.
RADIATOR
– Directs coolant through a series of fins or baffles so outside air
can remove excessive heat from coolant.
FAN CLUTCH
– Regulates use of fan to control engine temperature fan to
belt driven pulley when conditions require additional cooling.
WATER PUMP
– Provides force to move coolant through engine.
FAN
– Provides force to pull air through radiator.
RADIATOR DRAINVALVE
– Permits coolant to be drained from radiator.
TRANSMISSION OIL COOLER HOSE
– Directs coolant to transmission oil
cooler.
ENGINE OIL COOLER
– Reduces heat of engine oil (M939/A1 series only).
TRANSMISSION OIL COOLER
– Reduces heat of transmission oil.
ENGINE OIL COOLER TO HEATER HOSE
– Directs coolant to personnel
water heater when shutoff valve is open (M939/A1 series only).
PERSONNEL WATER HEATER
– Provides heat for cab and personnel.
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