Cooling System -807640157

TM 9-2320-312-24-2

Testing and Adjusting Section

Cooling System

4. Check for air in the cooling system. Air can

enter the cooling system in different ways. The

following items are some of the most common

causes for air in the cooling system:

i01389751

Cooling System - Check

Filling the cooling system incorrectly

(Overheating)

Combustion gas leakage into the cooling

system

SMCS Code: 1350-535

Loose hose clamp

Above normal coolant temperatures can be caused

by many conditions. Use the following procedure

Combustion gas can get into the system through

to determine the cause of above normal coolant

the following conditions: inside cracks, damaged

temperatures:

cylinder head, and damaged cylinder head

gasket. A loose hose clamp can allow air into the

cooling system during the cooldown period. Air

in the cooling system causes a reduction in the

cooling capacity of the coolant.

Personal injury can result from escaping fluid un-

der pressure.

5. Check the fan drive system. A fan drive system

that is not turning at the correct speed can cause

If a pressure indication is shown on the indicator,

push the release valve in order to relieve pressure

improper air speed across the radiator core. The

before removing any hose from the radiator.

lack of proper air flow across the radiator core

can cause the coolant not to cool to the proper

temperature differential.

1. Check the coolant level in the cooling system.

Refer to Operation and Maintenance Manual,

6. Check the water temperature gauge. A water

"Cooling System Coolant Level - Check". If

temperature gauge which does not work correctly

the coolant level is too low, air will get into the

will not show the correct temperature. Refer to

cooling system. Air in the cooling system will

Testing and Adjusting, "Cooling System - Test".

cause a reduction in coolant flow and bubbles in

the coolant. Air bubbles cause a reduction in the

7. Check the sending unit. In some conditions, the

cooling of engine parts.

temperature sensor in the engine sends signals

to a sending unit. The sending unit converts

2. Check the quality of the coolant. The coolant

these signals to an electrical impulse which is

should have the following properties:

used by a mounted gauge. If the sending unit

malfunctions, the gauge can show an incorrect

Color that is similar to new coolant

reading. Also if the electric wire breaks or if the

electric wire shorts out, the gauge can show an

Odor that is similar to new coolant

incorrect reading.

Free from dirt and debris

8. Check the radiator.

If the coolant does not have these properties,

a. Check the radiator for a restriction to coolant

drain the system and flush the system. Refill

flow. Check the radiator for debris, for dirt, or

the cooling system with the correct mixture of

for deposits on the inside of the radiator core.

water, antifreeze, and coolant conditioner. Refer

Debris, dirt, or deposits will restrict the flow of

to Operation and Maintenance Manual, "General

coolant through the radiator.

Coolant Information".

b. Check for debris or for damage between

3. Check the coolant mixture of antifreeze and

the fins of the radiator core. Debris between

water. The mixture should be approximately 50

the fins of the radiator core restricts air flow

percent water and 50 percent antifreeze with

through the radiator core. Refer to Testing and

3 to 6 percent coolant conditioner. Refer to

Adjusting, "Cooling System - Inspect".

Operation and Maintenance Manual, "General

Coolant Information". If the coolant mixture is

c. Check for missing radiator baffles or for

incorrect, drain the cooling system and flush the

damaged radiator baffles. Radiator baffles

cooling system. Refill the cooling system with the

prevent recirculation of air around the sides

correct mixture of water, antifreeze, and coolant

of the radiator. A missing radiator baffle

conditioner.

or a damaged radiator baffle raises the

temperature of the air that goes through the

radiator.