Combustion engines not only generate energy in the form of drive energy during operation, but also a lot of heat. This must be dissipated by cooling so that engine components are not damaged by overheating. In addition, the cooling system enables the engine to operate in the optimum temperature range, thus ensuring low emissions. You can find all important information on engine cooling here.

Function of the cooling system – this is how heat is dissipated from the engine

To ensure effective cooling, every modern combustion engine is equipped with a cooling system for the engine. This is almost always a water cooling system. Cooling water is directed through fine channels through the engine block and cylinder head to carry heat away from the engine and lower the engine temperature. After the coolant in the radiator has cooled down, it is returned to the engine.

Engine cooling in different driving situations

The cooling system in the car works differently depending on the driving situation, and adjusts the cooling capacity accordingly. This makes it possible to always run the engine at the optimum operating temperature. When driving fast on country roads or on the motorway, a lot of air gets into the radiator in the front of the vehicle. Sometimes this air flow is already sufficient to be able to dissipate the heat.

Engine cooling during traffic jam or stop-and-go

If, on the other hand, the vehicle is stuck in a traffic jam or in stop-and-go traffic, an additional fan ensures that enough air can flow through the radiator. The same applies whenever a particularly large amount of heat needs to be dissipated from the engine. This can be the case in summer, for example, when temperatures rise outside. The engine temperature can also rise unusually when driving uphill.

Low and high temperatures

If, on the other hand, the temperature outside the vehicle is particularly low, for example in winter, the fan is not used. The cooling circuit to the radiator is also only activated when the engine has reached its operating temperature. If the engine overheats unexpectedly, it can be helpful to switch on the heating in the car and open the windows. In this way, further heat is dissipated via the heater’s heat exchanger.

Air cooling versus water cooling

In addition to engine cooling by means of a cooling circuit, cooling can also be realised by means of air. Probably the best-known car with air cooling is the Volkswagen Beetle. Porsche also continued to use this type of engine cooling for a long time with the 911 model. Cooling by means of air flow has several advantages over engine cooling with coolant. Among other things, considerably fewer components are needed than with liquid cooling.

Cooling by means of air flow

In vehicles with air cooling, the ambient air is drawn in by a mechanically driven cooling fan and directed over the engine components to be cooled. To enable better heat transfer, engine housings, cylinders or cylinder heads are provided with cooling fins.

Advantages and disadvantages of air-cooled engines

Essential components of the water cooling system such as the radiator, water pump and radiator hoses are omitted in air-cooled engines. Consequently, these components cannot wear out or break down. Since there is no cooling water, the water cannot freeze either. However, air cooling is less effective than engine cooling by means of coolant. Engines with low emissions can therefore only be realised with liquid cooling.

Overview of essential engine cooling components

• Radiator: The radiator is usually mounted on the front of the vehicle behind the radiator grille. It contains small pipes through which the coolant flows. Fine fins facilitate the exchange of heat from the radiator fluid to the ambient air.
• Water pump: The water pump ensures that the cooling water circulates continuously in the cooling circuit when the engine is running. Depending on the vehicle, the pump is driven directly by the engine, via a toothed belt or via the V-belt. There are also electric pumps.
• Thermostat: The thermostat in the cooling system regulates the engine cooling. Only when the engine has reached an optimum operating temperature does the valve open. The cooling water then flows through the entire cooling system with the radiator at the front of the vehicle.
• Heat exchanger: The heat exchanger of the heater ensures that the interior of the vehicle is always at a comfortable temperature in winter. The cooling water flows through this component and can release the heat into the passenger compartment by means of a fan.
• Radiator fan: The radiator is equipped with one or more radiator fans. These fans ensure a greater air flow through the radiator when required, even without airstream. They are usually electrically driven, on some models also mechanically.
• Expansion tank: The closed cooling system of modern vehicles usually has an external expansion tank. This part can be found in the engine compartment and functions as an expansion tank. Often, the correct coolant level can also be read here.
• Coolant: The coolant itself is also important in an internal combustion engine with liquid cooling. It ensures rapid removal of the heat generated during engine operation. As a rule, a mixture of water and an additive is used as the coolant.

These errors can occur in the cooling system

If there are problems with the engine cooling, defective components are almost always the cause. Often there is a leak in the cooling system from which coolant is escaping. The radiator hoses, the radiator itself or the water pump may be leaking. The result is an insufficient coolant level.

Operating temperature is not reached or exceeded

If the cooling water temperature rises sharply, a defective thermostat or a broken radiator fan are possible causes. If the engine is slow to reach operating temperature, the thermostat may be stuck. A defective cylinder head gasket can also be responsible for the loss of cooling water if the water enters the combustion chamber.

5 tips to avoid problems with the cooling system

1. Check the cooling system: Many components of the cooling system are visible from the engine compartment. This makes it easy to check the components for leaks. An occasional look under the bonnet is worthwhile to detect leaks and prevent damage.
2. Use suitable coolant: The coolant used in the cooling system does not only consist of water, but is mixed with a suitable additive. Often, manufacturers prescribe a specific coolant additive that contains antifreeze as well as corrosion protection.
3. Check antifreeze: The antifreeze added to the cooling water can become less effective over time. This is especially the case if water has been added once. The antifreeze can be checked with an antifreeze tester so that it can be supplemented if necessary.
4. Do not postpone repairs: Defects in the cooling system can quickly lead to damage to the engine. If a defective part is detected, or if water under the engine compartment indicates a leak, the repair should be carried out promptly.
5. Have the engine serviced: A maintenance of the car or an inspection of the engine in the workshop also includes the cooling system. All important components for engine cooling are inspected by the specialist and checked for defects.

Buying and replacing spare parts for the cooling system

Numerous parts of the engine cooling system such as the radiator, fan, expansion tank or radiator hoses are easy to replace. For the water pump, the effort depends on the installation position and drive. It is important to bleed the cooling circuit after replacing parts and to top up the coolant accordingly. Original components are particularly precise and can be easily selected and bought used at Autoparts24.