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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
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
3-103

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