TM 9-2320-273-20
Section XII COOLING SYSTEM
2-31. INTRODUCTION.
The cooling system is identical in all M915 thru M920 vehicles, The system provides coolant
for the engine block, oil cooler, aftercooler, fuel injectors, and air compressor.
2-32. COMPONENTS AND PIPING ARRANGEMENT.
1.
THERMOSTAT DEAERATION LINE. Escape route for air trapped in radiator top or
thermostat housing.
2.
RADIATOR IN LET HOSE. Channels hot coolant into radiator when thermostat is open.
3.
ENGINE SHUNT LINE. Allow air bubbles from coolant in pump to escape into radiator,
to prevent pump cavitation.
4.
RADIATOR CAP. Closes off filler opening and keeps system under pressure up to a
maximum of 10 psi.
5.
RADIATOR. Coolant is circulated through a series of fins and baffles so that outside
air flow can dissipate heat.
6.
OIL COOLER. Engine coolant circulates through internal tubes of cooler and carries
away heat from engine.
7.
AFTERCOOLER. Coolant flowing through core cools hot air entering intake manifold
ports from turbocharger.
8.
WATER LINE. Carries water under pressure from block to aftercooler.
9.
WATER LINE. Carries hot water from air compressor to thermostat housing.
10.
WATER LINE. Carries coolant from water pump to air compressor.
11.
ACCESSORY DRIVE. Powers the fan and water pump.
12.
FAN. Forces air through radiator to control coolant temperature.
13.
FAN CLUTCH. Air pressure from actuator engages fan when coolant temperature rises
above 190°F (88°C).
14.
THERMOSTAT. Shuts off coolant flow to radiator until temperature reaches 185°F
(85°C). Coolant is then directed through radiator inlet hose to the radiator.
15.
FAN CLUTCH ACTUATOR. When coolant temperature rises above 190°F (88°C),
actuator directs compressed air into fan clutch causing fan to engage.
16.
WATER MANIFOLD. Collects coolant from cylinder heads and directs it to thermostat
housing.
2-30
