COOLING SYSTEM
position of the cap, it should be possible to depress the cap
approximately 3mm (1/8"). The depression can be adjusted by
bending the prongs on the cap. Care should be taken when
bending the prongs to ensure the cap is not too loose, as this
would prevent proper sealing. Then slowly continue to turn
cap counterclockwise until you can remove it.
NOTE - When removing the cap, loosen it slowly and then
pause to allow the pressure to bleed. This will avoid
possible burning by hot water or steam.
Figure 2. - Radiator Cap (Pressure Type)
Continuous Deaeration Cooling System
The continuous deaeration cooling system used on some IH
chassis, (Figure 3) is designed to keep the cooling system free
of trapped air, vent the cooling system during the filling
operation and completely vent the system in about five to ten
minutes. The deaeration system also aids in rapid warm-up of
cold engines.
Why are we concerned about the air in the cooling system? It
has been found that air trapped in the cooling system will
hasten corrosion in the system. Air expands more than water
when heated and increases the expansion loss through the
overflow pipe. More important is the possible loss of the water
pump prime due to excessive amount of air, resulting in
complete stoppage of coolant flow.
It has been found that when coolant flow stops even for a short
period, the engine is put in immediate danger.
When engine is operating at full throttle, the piston rings can
scuff, score or seize in as quickly as 30 seconds after the
coolant flow stops. Even if coolant is present, boiling, at the
points of maximum heat transfer, will occur. The transfer of
heat will be reduced, and the temperature will rise high enough
to destroy the lubricant oil film in the cylinder. The piston will
also expand as its temperature is raised, and scoring can
occur.
Figure 3. - Continuous Deaeration System
This damage may not be immediately noticed, and the engine
will continue to operate. But this overheating can shorten the
service life of the engine, resulting in high oil consumption,
excessive blowby, or piston scoring especially on engines
which have accumulated high mileage (200, 000 to 400, 000
miles).
A properly designed deaerated cooling system must have the
ability to deaerate when the engine is cold, when the
thermostat is closed, as well as when the engine reaches
operating temperature. To accomplish this, the radiator top
tank is designed with two sections divided by a baffle (Figure
4). The core of the radiator is vented through a tube which
extends above the coolant level in the upper portion of the
tank. This tube provides the vent needed for the core (Figure
2).
A make-up line is provided from the upper portion of the tank
to the suction side of the water pump, to supply coolant to the
cooling system. Another vent line is connected from the
engine side of the thermostat housing to the top tank above
the coolant level. This line provides a vent for the engine.
CTS-4181
Page 5
