CAUTION - CORRECT THIS CONDITION IMMEDIATELY OR
SERIOUS DAMAGE TO ENGINE WILL RESULT.
May be caused by any of the following:
Radiator or other parts of cooling system clogged with
rust or scale.
Grille or bug screen clogged.
Radiator core fins damaged.
Thermostat defective - stuck closed.
Water pump leaking air into system.
Radiator hose collapsed or rotting inwardly.
Radiator pressure cap defective.
Cylinder head loose, causing exhaust gas leakage
into cooling system.
Water pump impeller corroded or loose on shaft.
Anti-freeze protection inadequate, causing partial
Boiling which may occur in a cooling system after the engine is
shut off even though it did not occur during operation is known
as after-boil. This condition, which usually happens to cooling
systems that need attention, occurs because the coolant is
still picking up heat from the engine and the heat is not being
dispersed by circulation through the radiator. Other causes of
after-boil are over-protection or use of high-temperature
thermostat with alcohol-type anti-freeze, improper installation
of the thermostat, or a thermostat that is operating improperly.
Foaming of coolant may also cause coolant loss. This occurs
only with a very dirty cooling system and under severe
operating conditions. Usually an air or exhaust leak in the
system contributes to foaming and this is caused by a faulty
gasket, leaky radiator hose or water pump seal. Foam is an
excellent insulator and can seriously interfere with proper
Evaporation reduces the amount of coolant in the system.
This is a common occurance where alcohol-base types of anti-
freeze are used. A faulty pressure cap may also be the cause
CAUSES OF OVERHEATING
Low coolant supply.
Leaks at any of the following: gaskets, hose
connections, water pump, radiator, heater, core
plugs, drain cock or plugs, cracked head or block.
Broken or loose fan belt.
Collapsed or clogged hose.
Defective pressure cap.
Worn or corroded impeller on water pump.
Radiator air flow obstructed.
Bent fan blade.
Improper or defective thermostat.
Clogged muffler or tail pipe.
Stiff re-built engine.
Low engine oil level.
CAUSES OF OVERCOOLING
Defective thermostat stuck open.
Short runs and intermittent driving.
TROUBLESHOOTING THE CONTINUOUS
DEAERATION COOLING SYSTEM
If the engine fails to reach normal operating temperature, the
following checks should be made to find the possible cause:
Visually inspect the thermostat to be sure it is the
correct thermostat and has the proper range.
Check the thermostat to make sure the valve is not
held open by foreign matter and that the thermostat
valve closes with a good seal.
Check the operation of the thermostat in a pan of
water. Heat the water. The thermostat should begin
to open at about 95°C (170°F). The thermostat
should be fully open at 102C (185F). At any
temperature below 95°C (170F), the thermostat
valve should be tightly closed.
The engine will not warm up properly if accessories
such as heaters, air compressors or cooling system
water filters are not connected in the proper manner.
These accessories should not be connected so that
the outlet coolant goes to the radiator core. These
units should not be connected to the make-up line,
because the make-up line will not be large enough to
carry the excess coolant.