COOLING SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
COOLING SYSTEM TEST - CONTINUED
Checking Filler Cap
N OT E
Pressure loss in cooling system can be caused by defective seal on radiator filler cap.
With engine cool, slowly loosen filler cap to release any pressure from cooling system and remove filler cap (TM 5-
Inspect filler cap seal. Check for damage to seal and sealing surface of radiator.
Remove any debris on cap, seal, or sealing surface of radiator.
Install filler cap on cooling system pressure tester.
Check pressure that opens filler cap.
Compare pressure to pressure rating marked on top of filler cap.
If filler cap is damaged, replace filler cap (TM 5-3805-291-10).
Cooling System Check (Overheating)
WARN I N G
DO NOT service cooling sysem unless engine has been allowed to cool down. This is a pressurized
cooling system and escaping steam or hot coolant may result in serious burns.
DO NOT remove cooling system ra iator cap when engine is hot. Allow engine to cool down.
Loosen cap and let any pressure out of cooling system, then remove cap. Failure to follow this
warning may result in serious burns.
Wear effective eye, hand, and skinprotection when handling coolants. Failure to do so may result
in injury to personnel.
If a pressure indication is shown on the indicator,push the release valve in order to relieve pres-
sure before removing any hose from the radiator.
N OT E
Above normal coolant temperatures can be caused by many conditions. Use the following procedure
to determine the cause of above normal coolant temperatures.
Check the coolant level in the cooling system (TM 5-3805-291-10). If the coolant level is too low, air will get into the
cooling system. Air in the cooling system will cause a reduction in coolant flow and bubbles in the coolant. Air bubbles
will keep coolant away from the engine parts, which will prevent the transfer of heat to the coolant. Low coolant level is
caused by leaks or incorrectly filling the radiator.
Check the mixture of antifreeze and water (WP 0020 00). The mixture should be approximately 50 percent water and 50
percent antifreeze. If the coolant mixture is incorrect, drain the system. Put the correct mixture of water and antifreeze in
Check for air in the cooling system. Air can enter the cooling system in different ways. The most common causes of air
in the cooling system are not filling the cooling system correctly and combustion gas leakage into the cooling system.
Combustion gas can get into the system through inside cracks, a damaged cylinder head, or a damaged cylinder head
gasket. Air in the cooling system causes a reduction in coolant flow and bubbles in the coolant. Air bubbles keep coolant
away from the engine parts, which prevents the transfer of heat to the coolant.