TM 9-6115-624-BD
Section III. LIQUID COOLING SYSTEM
6-6.
Coolant Substitutes . During performance of repairs, or as a result of leakage, the coolant may become lost. A
liquid cooled engine cannot operate for long without coolant. When normal coolants are not available a substitute may
be used. Any liquid, except gasoline or jet fuels, can be used as a substitute but some liquids will deteriorate the cooling
system rubber components. Petroleum products will not transfer the heat as efficiently as a water-based coolant, but will
work if nothing else is available. Old engine oil or fluids drained from damaged vehicles, transmission oil, hydraulic
systems, may be a possible source of fluids. The cooling system must be drained and flushed as soon as possible if
petroleum-based flu ids are used.
6-7.
Thermostat, Stuck. The thermostat regulates the engine operating temperature, from 180 to 195 degrees F., by
controlling coolant flow through the engine. When the thermostat is stuck in the closed position it prevents coolant from
circulating and causes engine overheating. BDAR repair is to remove the thermostat and operate the generator. If the
thermostat is stuck in the open position or removed, it may degrade engine performance and increase fuel consumption.
6-8.
Engine Coolant, Frozen . During cold weather, inadequate antifreeze protection will cause the coolant to freeze.
Care must be taken when thawing the cooling system that further damage is avoided. The water pump may be unable to
turn which will damage drive belts as well as the pump itself. The thawing procedure must include frequent inspections
for leaks which will indicate cracked or broken components. Engine temperature must also be monitored to prevent
overheating damage.
a. Limitations.
None if engine is left running or antifreeze protection is upgraded.
b. Personnel/time required.
2 soldiers/0.5-1.0 hours
c.
Materials/tools.
d. Procedural Steps.
(1) Gain access to radiator and power pack.
(2) Inspect for amount of ice and obvious cracks in coolant system components.
(3) If coolant is solid, remove or disengage the water pump drive belts.
(4) Start the engine and allow to warm up, but not get hot.
(5) Shut down the engine and allow the heat to radiate into and melt the ice.
(6) Attempt to turn water pump pulley.
(7) When the water pump pulley can be turned reinstall the drive belts.
(8) Restart the engine and allow to warm up but not overheat.
(9) Other options: Route air from fuel vehicle heater over the radiator. Route a vehicle's exhaust over the
radiator.
Record the BDAR action taken. When the mission is completed, as soon as practicable, repair the generator using
standard maintenance procedures.
6-4
