A vehicle's cooling system is designed to dissipate the heat created by combustion and keep the engine running at an optimal temperature for good fuel economy. The heat is dissipated to the atmosphere through the radiator and to the passenger department through the heater when the heat is turned on. This is why if a vehicle starts to run too hot, turning on the heater will sometimes bring the temperature down.
The main components of the cooling system are the radiator, water pump, thermostat, cooling fan, heater, hoses and the coolant liquid.
The radiator is composed of two tanks with tubes and cooling fins running between them. The purpose of the radiator is to dissipate the heat from the engine coolant liquid. It accomplishes this by circulating ambient air through the cooling fins as the liquid coolant circulates through the radiator.
The water pump is made up of an impeller which pushes the coolant liquid through the system. It is usually driven by the engine drive belt or timing belt via a pulley on the opposite end of the shaft from the impeller.
The thermostat is a heat activated valve which regulates the temperature of the coolant. It remains closed until the engine is warmed up, then opens and closes to keep the coolant within a narrow temperature range. If a thermostat remains open the temperature gauge will read low and the heater will produce very little heat.
A cooling fan is either a belt driven or electric fan. Its function is to move air through the radiator when the vehicle is stopped or moving slowly. Both types of fans are heat activated and only operate when the coolant reaches a certain temperature.
The heater is designed like a radiator and mounted in the passenger compartment. When the heater is turned on the fan pulls air through the heater and transports heat into the passenger compartment.
Radiator and heater hoses connect the radiator and heater to the engine.
The coolant liquid is known as antifreeze and the most commonly used type in automotive systems is ethylene glycol. It is mixed 50-50 with water and will resist freezing to -40 degrees F and will withstand temperatures up to 250 degrees F without boiling. It also contains rust inhibitors and lubricants. Newer longer lasting types of antifreeze are used in many late model cars.
Cooling system maintenance is extremely important because failure of any component could cause severe overheating and expensive engine damage. As antifreeze gets old, the rust inhibitors begin to separate out into solids which in turn can clog the radiator. As the lubricating qualities in the antifreeze begin to wear out, the water pump can begin to leak. With age, the hoses will begin to split from the inside. This isn’t apparent from a visual inspection unless they are bulging, but by squeezing the hose, an interior crack or softness may be discovered. Regular inspection of the cooling system and flushing the coolant every 30, 000 to 60,000 miles is essential to the reliability of the system.