In a modern engine, only around one third of the heat produced during combustion is converted into mechanical energy to drive the vehicle. The rest is dissipated mainly be the exhaust system and through the cooling system.

The cooling system removes around one third of this heat by circulating coolant through the engine. (Coolant is a mixture of water and a special liquid concentrate that helps to inhibit corrosion forming in the engine.) Heat is removed by the radiator which uses air to cool the coolant.

The other important function of the cooling system is to keep the engine operating at a constant temperature at which peak operating efficiency is achieved.

Most modern systems are pressurised to raise the boiling point of the coolant so EXTREME CAUTION should be exercised when carrying out maintenance, as serious scalding could result. DO NOT REMOVE THE RADIATOR CAP WHILE THE ENGINE/COOLING SYSTEM IS HOT.

If driving in cold conditions you may need to use anti-freeze in the cooling system. Always follow the vehicle manufacturer’s directions when using anti-freeze and coolant.

The main cooling system components are:

The main purpose of the radiator is to reduce the temperature of the coolant. This is achieved by directing the coolant through thin metal tubes and using cool air passing through these tubes to cool the coolant.

 

This has two main purposes. The first is to be the access point to which coolant can be added to the system and resealed afterwards. The second is to act as a pressure regulator, allowing pressure to build up and be maintained at a pre-determined setting, which increases the boiling point of the coolant.

 

Coolant expands as the temperature of the engine increases. When this occurs in the cooling systems the excess coolant flows into the overflow or expansion bottle. Subsequently, as the coolant cools down the coolant is drawn back into the cooling system thus ensuring no air is introduced into the system.

 

Radiator hoses carry the coolant between the radiator and the engine. The cooling system works under pressure therefore the hoses need to be securely held by clamps to prevent coolant leakage.

 

When caught at lights or in traffic, it is necessary to maintain airflow through the radiator. Therefore, in these conditions, air needs to be drawn through mechanically. This is done by the fan. The fan can be driven by the engine, via a fan belt and pulley, or electrically.

 

To be able to get engines to run at peak efficiency, engine designers need to be able to control the minimum operating temperature, this is controlled by the thermostat. The thermostat acts like a valve restricting coolant flow when the engine is cold, allowing the engine to reach operating temperature quickly. As the temperature of the engine increases so does the coolant flow.

 

Modern vehicles are designed to operate at maximum efficiency at a certain temperature, removal of the thermostat from the system will cause the engine to operate at an undesirable temperature, resulting in possible loss of performance and possible engine sludging and wear.

 

For the cooling system to be effective there needs to be a constant circulation of coolant. This is achieved by using a mechanical pump, engine driven by means of the alternator or timing belt, to circulate coolant through the system.

 

The engine block has water jackets in which coolant flows absorbing heat which is transferred via the hoses to the radiator. These water jackets allow coolant to be able to flow throughout the engine, hence removing engine heat. When engine blocks are manufactured, casting residue is removed via preset holes which are sealed by inserting small metal discs called welsh plugs.

 

Many engine failures can be attributed to neglect of the cooling system and could be easily avoided. The following check points should help you to avoid unnecessary engine damage:

What does it mean if I have to continually top up the coolant level?

If you are continually topping up the coolant level, take your vehicle to your mechanic as soon as possible. A simple fault may turn into a major engine repair if left unattended.

 

Check the fan belt and tighten the house clamps on a regular basis. Your owners handbook will indicate the frequency and method, (usually every 6 months or before a long trip).

Most importantly, keep your eye on the temperature gauge. Pull over when the temperature rises above the normal indicator, not when the car stars to run rough or stalls. If this occurs, it’s usually too late and an expensive engine repair may be needed.