Engine Coolant Frozen

TM 5-3835-222-BD

6-7. Thermostat Stuck. The thermostat regulates the engine operating temperature, from 180 to

195 degrees farenheit, 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 equipment. 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 so 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.

Limitations:

None if engine is left running or antifreeze protection is upgraded.

Personnel/Time Required:

2 soldiers - 30 minutes - 1.0 hrs.

Procedural Steps:

a. Gain access to radiator and powerpack.

b. Inspect for amount of ice and obvious cracks in coolant system components.

c. If coolant is solid, remove or disengage the water pump drive belts.

d. Start the engine and allow to warm up, but not get hot.

e. Attempt to turn water pump pulley.

f. Shut down the engine and allow the heat to radiate into and melt the ice.

g. When the water pump pulley can be turned, reinstall the drive belts.

h. Restart the engine and allow to warm up, but not overheat.

Other Options:

Route air from fuel operated vehicle heater over the radiator.

Route another vehicle's exhaust gases over the radiator.

Record the BDAR action taken. When the mission is completed, as soon as practicable, repair the

equipment using standard maintenance procedures.

6-9. Radiator Leaking. Radiator leaking may be detected by low coolant levels. Obvious wet areas

or overheating will indicate that the coolant level must be checked. The repair procedure used is

dependent on the size of the hole(s) causing the leak. The following procedures provide options to

stop or reduce the leakage rate.

6-3