TOPIC 1. COOLING SYSTEM DESCRIPTION

TM 10-3930-644-14&P

TOPIC 1. COOLING SYSTEM DESCRIPTION

The function of the cooling system is to prevent the

Teledyne Continental L-Head gasoline engines operate

temperatures in the combustion chamber, which may

most efficiently with water temperatures of 180 to

reach as high as 40000F., from damaging the engine

200F; the thermostat and bypass hose are used to

and, at the same time, keep the operating temperatures

control these temperatures.

within safe limits.

Before a cold engine reaches operating temperature, the

Maintaining the cooling system efficiency is important, as

thermostat valve is closed, passage to the by-pass hose

engine temperatures must be brought up to and

is open, and the coolant recirculates through the engine

maintained within satisfactory range for optimum

block only.

operation; however the system must be kept from

overheating, in order to prevent damage to valves,

This provides for both rapid and even temperature

pistons and bearings.

increase of all engine parts during the warm-up period.

When proper temperature is reached, the thermostat

See Figure 1-1. The system coolant is water which is

valve opens and allows the coolant to circulate through

force-circulated by a water pump. A thermostat and a

both the engine and the radiator.

by-pass hose, which form part of the system, serve to

direct coolant flow through the engine only, or through

Water has always been the most commonly used

the engine and the radiator.

coolant for internal combustion engines because it has

excellent heat transfer ability and is readily obtained

Coolant from the water pump is first directed in the block

everywhere. Like all liquids it expands when heated, the

against the exhaust valve seats and into passages

rate of expansion being 1/4 pint per gallon when the

connecting the cylinder head. This method provides the

temperature is raised from 40 to 180 F.

coldest water reaching the parts subjected to the highest

temperatures.

For example: If a 4 gallon cooling system is filled

completely full of water at 40F, 1 pint will be lost

The cylinder walls, in turn, are cooled their full length by

through the radiator overflow pipe by the time the water

convection currents only, which keep the cylinder barrels

temperature reaches 180F.

at a more uniform temperature and, thereby, reduce

crankcase oil dilution and sludge formation.

Upon

Water boils at 212F under atmospheric pressure at sea

leaving the cylinder head, the coolant enters the

level. This pressure becomes less at higher altitudes

thermostat housing in which is mounted the bypass type

and the reduced pressure causes water and other liquids

thermostat. Coolant passage to the radiator is controlled

to boil at a lower temperature. The chart shown in

by the thermostat. Upon being discharged from the

Figure 1-2 shows the effect on boiling point of water and

thermostat housing, the coolant enters the radiator,

anti-freeze solution.

where it is cooled before re-entering the engine through

the water pump.

Figure 1-1. Cooling System, Cross Sectional View

R-155-1

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