Cooling System - Inspect

TM 9-2320-312-24-2

Testing and Adjusting Section

15. Check the shunt line. The shunt line must be

i01390078

submerged in the expansion tank. A restriction

Cooling System - Inspect

of the shunt line from the radiator top tank to the

engine water pump inlet will cause a reduction

SMCS Code: 1350-040

in water pump efficiency. A reduction in water

pump efficiency will result in low coolant flow

Cooling systems that are not regularly inspected are

and overheating.

the cause for increased engine temperatures. Make

a visual inspection of the cooling system before any

16. Check the water temperature regulator. A water

tests are performed.

temperature regulator that does not open, or

a water temperature regulator that only opens

part of the way can cause overheating. Refer

to Testing and Adjusting, "Water Temperature

Regulator - Test".

Personal injury can result from escaping fluid un-

der pressure.

17. Check the water pump. A water pump with

a damaged impeller does not pump enough

If a pressure indication is shown on the indicator,

coolant for correct engine cooling. Remove

push the release valve in order to relieve pressure

the water pump and check for damage to the

before removing any hose from the radiator.

impeller. Refer to Testing and Adjusting, "Water

Pump - Test".

1. Check the coolant level in the cooling system.

Refer to Operation and Maintenance Manual,

18. Check the air flow through the engine

"Cooling System Coolant Level - Check".

compartment. The air flow through the radiator

comes out of the engine compartment. Ensure

2. Check the quality of the coolant. The coolant

that the filters, the air conditioner, and similar

should have the following properties:

items are not installed in a way that prevents the

free flow of air through the engine compartment.

Color that is similar to new coolant

19. Check the aftercooler. A restriction of air flow

Odor that is similar to new coolant

through the air to air aftercooler (if equipped)

can cause overheating. Check for debris or

Free from dirt and debris

deposits which would prevent the free flow of

air through the aftercooler. Refer to Testing and

If the coolant does not have these properties,

Adjusting, "Aftercooler - Test".

drain the system and flush the system. Refill

the cooling system with the correct mixture of

20. Consider high outside temperatures. When

water, antifreeze, and coolant conditioner. Refer

outside temperatures are too high for the rating

to Operation and Maintenance Manual, "General

of the cooling system, there is not enough of a

Coolant Information".

temperature difference between the outside air

and coolant temperatures.

3. Look for leaks in the system.

21. Consider high altitude operation. The cooling

Note: A small amount of coolant leakage across

capacity of the cooling system goes down as

the surface of the water pump seals is normal.

the engine is operated at higher altitudes. A

This leakage is required in order to provide

pressurized cooling system that is large enough

lubrication for this type of seal. A hole is provided

to keep the coolant from boiling must be used.

in the water pump housing in order to allow this

coolant/seal lubricant to drain from the pump

22. The engine may be running in the lug condition.

housing. Intermittent leakage of small amounts of

When the load that is applied to the engine is

coolant from this hole is not an indication of water

too large, the engine will run in the lug condition.

pump seal failure.

When the engine is running in the lug condition,

engine rpm does not increase with an increase

4. Ensure that the airflow through the radiator does

of fuel. This lower engine rpm causes a reduction

not have a restriction. Look for bent core fins

in air flow through the radiator. This lower engine

between the folded cores of the radiator. Also,

rpm also causes a reduction in coolant flow

look for debris between the folded cores of the

through the system. This combination of less air

radiator.

and less coolant flow during high input of fuel

will cause above normal heating.

5. Inspect the drive belts for the fan.

6. Check for damage to the fan blades.