The radiator is one of the car's most important components because it is essentially what keeps the engine from overheating.
Inside of an engine, combustion is constantly happening. Fuel and air are injected into the cylinders and the spark plugs ignite them to create the force necessary to drive the pistons and in turn, drive the crankshaft. As you can imagine, when this happens thousands of times per minute, the engine's overall temperature can get pretty hot. Besides the area occupied by the valves, cylinders, and the crankshaft, an engine is mostly empty space. This is to accommodate engine coolant, which passes through the engine to keep it at a good operating temperature.
An engine has to be able to handle both extreme cold (less then freezing) and extreme heat (well over 200° F). As a result, there needs to be a cooling fluid that can handle this temperature range. Water is a good fluid for the purpose of cooling the engine, but in order to keep its freezing point low it has to be mixed with an anti-freeze solution. To keep its boiling point down even further, the car's cooling system is pressurized, meaning that no liquid is allowed to escape.
So, during the engine's operation there is always coolant flowing around the cylinders, exhaust valves, and engine block, but that still doesn't explain how the coolant remains cool. This is where the radiator comes in. A radiator is an aluminum chamber, with a series of tubes running through it in a parallel arrangement. Attached to the tubes are metal fins which conduct and dissipate the heat of the liquid inside.
To ensure that the engine's temperature is neither too high nor too low, a thermostat is positioned in the cooling system to monitor the temperature. If the engine's temperature is fairly low, the coolant will circulate inside of the engine, but not pass through the radiator. Inside the thermostat is a cylinder containing a wax substance that melts at around 180° F. When this happens the cylinder expands, allowing the coolant to pass through the radiator.Radiator Flush Ottawa