TM 5-4320-300-14
Table 4-2. Organizational Maintenance Troubleshooting - Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 2. Check for malfunctioning thermostat.
WARNING
Hot coolant may be released when radiator cap is
removed. Allow engine to cool before removing
cap. Open cap part way to ensure that pressure in
cooling system is released, then remove cap.
Remove radiator cap and open draincock at bottom of radiator. Drain cooling system to a level
where coolant is below the thermostat. Disconnect radiator hose at water outlet elbow after
loosening clamp.
CAUTION
Remove water outlet elbow slowly to avoid damaging
gasket.
Remove bolts, lockwashers, water outlet elbow, gasket, and thermostat. Check operation of the
thermostat by immersing it in a container of hot water. Place a thermometer in the container, but
do not allow it to touch the bottom. Agitate the water to maintain an even temperature
throughout the container. As water is heated, the thermostat should begin to open when
temperature reaches 167-172°F (75-78°C). The opening temperature is stamped on the
thermostat. Thermostat should be fully open at approximately 190-192°F (88-89°C).
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