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What is the radiator/what does it do?

A car's radiator is a central part of the engine's cooling system. Responsible for removal of heat from the engine coolant, the radiator system cools the liquid by allowing fresh external air to pass over a network of thin pipes, losing heat to the atmosphere.

Driven by the water pump, the coolant circulates around the cooling system travelling through the engine and out via hoses or pipes to the radiator. The radiator acts as a heat exchange, removing unwanted heat from the coolant before passing it back to the engine where it then runs back around the system.

Getting into the details of the radiator

As described above the key component of the radiator system is the radiator itself, which is a heat exchange responsible for removal of heat from the coolant. It is generally constructed of sheet metal, usually aluminium but sometimes copper or brass, pressed and soldered to create a network of thin pipes or cores. Each core is separated with gaps, allowing air to pass between them. This creates a large surface area when compared to the volume of coolant in the radiator, which allows for efficient reduction in temperature. The pipes or cores are linked by header tanks at either end of the radiator unit. The top hose from the engine connects to the top of one header tank and the cooled coolant exits from the bottom of the opposite header, via the bottom hose, before returning to the engine. Some header tanks have a removable radiator cap to allow for topping up of the coolant. Radiators without removable caps are generally topped up via a header tank which is located within the engine bay and connected via rubber tubing or hose.

The radiator is mounted across the front of the engine bay. It is suspended within a support panel which is mounted to the inside of the front panel of the vehicle body.

In between the radiator and the bonnet grille is another key component of the radiator system - the radiator fan. This fan blows fresh air across the radiator's cores helping to cool the coolant. The radiator fan can be belt or motor driven and is usually located within a plastic housing or cowling to ensure that air is funnelled correctly onto the radiator's cores. Most modern car's use an electric motor driven fan, which is controlled by a radiator temperature switch and motor relay, to ensure the fan is activated when the coolant exceeds a specified temperature.

What if something goes wrong with the radiator?

There are several issues that can occur with the radiator system. Radiator specific faults include radiator leaks, leaky fittings or perished hoses. If the radiator has a leak you may notice bubbles escaping or steam billowing out of the radiator and coolant puddling under the car's engine bay. Other signs include the engine running hotter than usual and dashboard warning lights. Radiators do gradually deteriorate and it's therefore important to maintain the correct coolant mixture as the additives contain rust inhibitors that prolong the units life.

Other problems with the radiator system can include failure of the temperature switch, motor relay or motor itself, preventing the fan from activating when required. Also the fan blades or cowling can become brittle due to the extremes of temperature.