TOPIC 1. COOLING SYSTEM

TM 10-3930-644-14&P

TOPIC 1. COOLING SYSTEM

A. DESCRIPTION

temperature exceeds 180 F, then the thermostat begins

to open and permits the coolant to flow into the radiator

The cooling system consists of the following component

where it is cooled by the belt-driven cooling fan. At

parts: the radiator, water pump and thermostat, the

approximately 200F, the thermostat will be completely

cooling fan and fan belt, the water passages in the

open and the coolant will flow at the maximum rate

cylinder block and head, and the necessary hoses and

through the radiator until the average temperature has

lines to complete the system.

been reduced and the thermostat closes.

The purpose of the cooling system is to carry off the

B. GENERAL MAINTENANCE

excess heat from the engine, and to hold the engine at

an efficient operating temperature. This is performed in

Proper cooling system maintenance

requires

the

the following manner:

observance of the following procedures:

The centrifugal water pump, which is driven by a "V" belt

1. Coolant: Keep sufficient cooling liquid in the

from the fan drive pulley, pulls the coolant from the

system, but do not overfill. A basic coolant is

bottom of the radiator and circulates it through the water

fresh, clean, soft water to which is added a 2%

passages in the engine block and cylinder head. The

solution of rust preventive soluble oil.

coolant then passes from the cylinder head of the engine

temperatures below 320F, the cooling system

through the thermostat and the upper radiator hose to

should be protected from freezing by adding a

the upper part of the radiator. The coolant then passes

sufficient quantity of a permanent type (glycol

from the top to the bottom of the radiator and is cooled

base) anti-freeze solution.

by the air flow pushed through the radiator core by the

cooling fan.

2. Cleaning: Drain, flush and refill the system

whenever an inspection reveals an accumulation

If the temperature of the coolant is less than 180 F, the

of rust or scale deposits. Always clean the

thermostat remains closed and the coolant is bypassed

cooling system seasonally, as well as before

back to the pump and is recirculated through the engine

and after using anti-freeze solutions.

without passing through the radiator. When the coolant

Figure 1-1. Coolant Flow Diagram (Typical)

M-155-1

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