MOTOR TRUCK SERVICE MANUAL
COOLING SYSTEM
GENERAL
9. When the vehicle is equipped with a heater
2. Hydrometers (Fig. 7) which are used to test the
connected to the cooling system, flush the
freezing protection of an antifreeze solution,
work on the principle of specific gravity or weight
heater, following same procedure as for radiator
of the antifreeze solution. They are simple to
core.
use provided they are used in the proper
10. After completing the flushing operation, clean out
manner.
When using the hydrometer, the
radiator overflow pipe, inspect the water pump,
solution must be warm (at least 110), the
clean the thermostat and the radiator cap control
temperature and level must be noted correctly,
valves. Check thermostat for proper operation
and the float must be able to move freely. Read
before installation. (See "Thermostat".)
only the hydrometer scale corresponding to the
11. Blow insects and dirt from radiator core air
type antifreeze solution in the radiator. Keep
passages, using water, if necessary, to soften
hydrometer clean inside and out and treat it with
obstructions.
the same care as given any other precision
Test Equipment
To aid the service man in maintaining the cooling
instrument.
system at top efficiency, various items of test equipment
NOTE: Hydrometers do not correctly register the
are available. Among these are the Cooling System
freezing protection of a mixture of methanol and glycol
Pressure Tester and the Hydrometer.
base antifreeze.
1. Cooling System Pressure Tester (Fig. 6)- This
Therefore, always flush the cooling system with
equipment may be used in detecting the hard to
thermostat removed before adding antifreeze for the
find leaks in the cooling system. Any leak from
winter.
cracked cylinder heads, warped cylinder heads
or blown gaskets whether internal or external
can be located easily and in a short time with the
pressure tester. Adapters are available with the
tester which permit the testing of radiators on
trucks having the cab forward or cab over engine
design (Fig. 6). Pressure caps can also be
tested with the pressure tester.
Fig. 6 Using Cooling System Pressure Tester
(SE-1870 Adapter)
Fig. 7 Using Hydrometer to Test Antifreeze Solution.
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