Singapore Car Guide: Let off steam

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Let off steam
The functions of the engine’s cooling system are to remove excess heat from the engine, to keep it operating at the most efficient temperature. Find out more about its mechanics.
By Goh Mei Yi
Published: October 13, 2007, CATS Classified in the Straits Times
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The functions of the engine’s cooling system are to remove excess heat from the engine, to keep it operating at the most efficient temperature, and to allow it to reach its ideal operational temperature in the shortest time possible.

The car’s cooling system
The components include a radiator, fan, water pump, thermostat, an overflow tank, water, coolant, and a series of connecting pipes and passageways. The system works by directing fluid past the hottest parts of your engine (the cylinder heads and valves) and redirecting the heated fluid out to the radiator, where the heat gets dissipated into the cooler atmosphere. The whole process then repeats.

Coolant
The fluid within your car’s cooling system contains water and coolant. The coolant consists of a green fluid that contains ethylene glycol, also known as antifreeze. This chemical extends the freezing and boiling point of water and also inhibits rust. However, even with ethylene glycol added, the coolant would still boil, so something more must be done to raise its boiling point.

Radiator cap
The boiling temperature of coolant is raised by pressurising the system, in the same way that the boiling point of water is increased in a pressure cooker. The radiator cap increases the boiling point of the coolant by about 25 degrees Celsius. The cap is actually a pressure release valve, and on cars it is usually set to 15psi.

When the pressure reaches 15psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank, which serves as a reservoir for the excess coolant that results from the water’s expansion when heated.

Never open your cooling system when it is still warm. Not only are the contents scalding hot, they’re also under incredible pressure.

Radiator
The radiator is a heat exchanger designed to transfer heat from the hot coolant to the cooler surrounding air. Located just behind the front grille, it is usually made of aluminium and consists of a series of tubes attached to many little metal fins. These fins increase the surface area of the radiator to cool the heated fluid more quickly.

Water pump and thermostat
A water pump drives the coolant into the engine block, where it makes its way through passages in the engine around the cylinders. The thermostat is located where the fluid leaves the engine.

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