ARMY TM 9-6115-604-12
NAVY NAVFAC P-8-633-12
4-58. TEST RADIATOR CAP. The radiator cap pressurizes the cooling system, thereby increasing the boiling point of
the coolant. Test radiator cap using a cap tester Cap setting should be approximately 7 psi (46.3 kPa) Check condition of
4-59. MAINTENANCE OF COOLANT THERMOSTAT. Four thermostats control the temperature of the coolant by con-
trolling the flow of coolant through the radiator.
Inspect. The thermostats (18, Figure 4-43) are inside the thermostat housing (20) mounted at the top front of the
engine. Inspect the thermostat housing for signs of coolant seepage.
Drain the engine and radiator in accordance with paragraph 3-12.
Loosen hose clamps (30, Figure 3-17) which secure radiator outlet hoses (31) to the thermostat housing
(20, Figure 4-43).
Remove capscrew (1) and lockwasher (2) to remove water filter assembly (3) from face of thermostat
housing (20). Remove and discard preformed packing (11).
Remove hexagon head capscrews (13 and 15) and lockwashers (14), to free thermostat housing (20) from
Remove thermostat (18) from rear of thermostat housing (20) Remove and discard housing gasket (17) and
thermostat seal (19).
Remove pipe plugs (16) as needed for repair or replacement.
To avoid Injury to personnel which may result from contact with hot engine coolant,
exercise caution during the following procedure.
Suspend thermostat in a container of antifreeze. Heat the solution slowly. Stir to maintain even heating.
Using a thermometer, monitor the temperature. The thermostat should open fully at 190°F (88C).
The coolant thermostat is not repairable If It does not meet the above test it must be replaced.