and attacks and coats the metallic surfaces of the cooling
system. This coating reduces the heat transfer. Cooling
system conditioners which contain these inhibitors must be
added to maintain corrosion protection. These conditioners
are available as a liquid or in a coolant filter.
Freezing Point C (F)
0° (+ 32)
- 7° (+20)
- 23° (-10)
29% (- 20)
- 69° (- 92)
As shown below, a further increase in antifreeze
volume increases the freezing point.
- 34° ( - 30)
-22° (- 8)
Figure 1. - Coolant Mixture Freezing Points
The two types of recommended conditioners are as
IH coolant conditioner is a complete inhibitor
system, of a non-chromate type, which provides
corrosion protection, pH control for maintaining
an acid free coolant and water softening to
prevent the formation of mineral deposits. It is
compatible with both water and IH anti-freeze
The coolant filters available on IH vehicles,
contain a blend of metaborate, tetraborate,
nitrite, nitrate, silicate, M.B.T., phenolphthalein,
and an organic polymer designed to provide
superior cooling system protection to that
obtained with either chromate or borate coolant
These coolant filters should only be used with
ethylene glycol type anti-freezes that do not contain
anti-leak additives. The anti-leak or stop leak
additives are removed by the water filter. This could
restrict coolant flow through the filter.
Soluble oil is not recommended for use on IH truck
engines as its use will reduce heat transfer. There
are no miracle additives that will increase heat
transfer or prevent overheating. Conditioned water is
still the best coolant.
COOLANT SYSTEM COMPONENTS
The following is a list of the major components making up the
cooling system. Points of inspection of each component are
covered in general terms.
This component is one of the most important, as this is where
most of the heat of the system is dissipated. The radiator is
made up of the following parts:
Top and Bottom Tank
Look for leaks, particularly where tank is soldered to core.
Vibration and pulsation from pressure can fatigue soldered
The sealing seat must be smooth and clean. Cams on the
filler neck must not be bent or worn, as this will not allow the
cap to seal properly. Ensure that the overflow tube is not
Because these are very small, they can become clogged, or
partially blocked, by rust and scale. The general condition of
the cooling system and operating temperature are indications
as to the cleanliness of the tubes. Another good test is to feel
the core for cold spots.
These thin metal sheets radiate, or pass off, the heat picked
up by the tubes. They should be kept free of bugs, leaves,
straw and other interference to allow free passage of air. Bent
fins should be straightened for maximum heat dissipation.
Radiator Cap (Pressure-Sealing Type)
Its purpose is to hold the cooling system under a slight
pressure, increasing the boiling point of the cooling solution
and preventing loss of the solution due to evaporation and
The cap (Figure 2) has a spring-loaded valve, the seat of
which is below the overflow pipe in the filler neck. This
prevents the escape of air or liquid while the cap is in position.
When the cooling system pressure reaches a predetermined
point, the cap valve opens and will again close when the
pressure drops below the predetermined point.
When removing the pressure type cap from the radiator,
perform the operation in two steps. Loosen the cap to its first
notch to raise the valve from the gasket and release the
pressure through the overflow pipe. In the first stage