Keeping Your Car's Cool Is Vitally Important

Sydney Morning Herald

Saturday July 29, 2000

By Jim Gibbons Jim Gibbons is executive director of the MotorTraders' Association of NSW

Whether it's cold or hot outside, your cat's cooling system is always working to keep the engine at its optimum operating temperature. Here's a brief summary of some cooling system components and what they do. The radiator cap maintains the cooling system's pressure. It has a regulating spring on it to hold the pressure and can release excess pressure developed by water expanding with heat. When water is kept under pressure this effectively increases the point at which the water will boil. More pressure gives a higher boiling point. The water in a car's cooling system is kept at a preset maximum pressure which is controlled by the radiator cap. On many systems you will find a bottle running to the radiator. The overflow bottle provides a place for storage of the coolant expelled from the cap. As the coolant warms and expands, water is expelled to the bottle. When the system cools, the water is drawn back into the radiator. This ensure no air gets into the radiator and cooling system. Cars fitted with overflow bottles require a radiator cap designed for the purpose. Ensure you have the right model if you purchase a new radiator cap. The water pump has the job of circulating water through the cooling system. It draws water from the inlet pipe, usually the bottom hose, and pumps water to the engine block out of the back of the pump. Water goes up to the head and is expelled from the top outlet on the engine to the top radiator hose, then goes back to the radiator for cooling. The fan on the engine assists air to flow when the vehicle is moving slowly or stationary. The system has a device to restrict flow until water comes to operating temperature. It is called a thermostat and is fitted in line, usually at the top water outlet that goes back to the top of the radiator. When the engine is cold the thermostat will be closed, stopping water circulating through the radiator and forcing it through a small bypass tube. The cooling system is under a great deal of heat stress. It is in your interests to replace hoses and fan belt before they break or split. The cost of that maintenance is cheap compared with damage created by a faulty cooling system. Because the coolant is constantly heated, then cooled, it becomes highly corrosive. You need to use an anti-corrosive additive. The most common is ethylene glycol, which provides protection from corrosion as well as reducing the freezing point and raising the boiling point of the water it's mixed with.