The temperature of the coolant circulating through the engine is lowered by the action of the radiator and the
fan. The radiator is mounted in front of the engine so that the fan will draw air through it, thereby lowering and
maintaining the coolant temperature to the degree necessary for efficient engine operation. Typical Radiator
Mounting (Fig. 1).
The life of the radiator will be considerably prolonged if a recommended-type coolant is used (refer to Coolant
To increase the cooling efficiency of the radiator, a metal shroud is placed around the fan. The fan shroud
must be fitted airtight against the radiator to prevent recirculation of the hot air drawn through the radiator. Hot
air which is permitted to pass around the sides or bottom of the radiator and is again drawn through the radiator
will cause overheating of the engine.
Figure 1. Typical Radiator Mounting (In-Line Engine)
Another cause of overheating is slippage of the fan drive belts which is caused by incorrect belt tension, worn
belts or worn fan belt pulley grooves, or the use of fan belts of unequal length when two or more belts are used.
The belt tension and condition of the belts should be checked periodically. Refer to Preventive Maintenance.
A radiator that has a dirty, obstructed core or is leaking, a leak in the cooling system, or an inoperative
thermostat will also cause the engine to overheat. The radiator must be cleaned, the leaks eliminated, and
defective thermostats replaced immediately to prevent serious damage from overheating.
The external cleanliness of the radiator should be checked if the engine overheats and no other causes are
The radiator should be cleaned whenever the foreign deposits are sufficient to hinder the flow of air or the
transfer of heat to the air. In a hot, dusty area, periodic cleaning of the radiator will prevent a decrease in
efficiency and add life to the engine.
The fan shroud and grille should be removed, if possible, to facilitate the cleaning of the radiator core.
An air hose with a suitable nozzle is often sufficient to remove loose dust from the radiator core. Occasionally,
however, oil may be present requiring the use of a solvent, such as mineral spirits, to loosen the dirt. The use
of gasoline, kerosene or fuel oil is NOT recommended as a solvent. A spray gun is an effective means of
applying the solvent to the radiator core. Use air to remove the remaining dirt. Repeat this process as many