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Cooling System

The cooling system in the car is exposed to a lot of strain. In summer, it has to keep the engine in an optimal temperature range even at high temperatures. In winter, the cooling system must not freeze under extreme conditions.  

What components does the cooling system of the engine consist of? How do defects manifest themselves and how are these remedied? 

On this page we want to give you some more detailed information about your vehicle’s complex cooling system. We hope you will find this page interesting. If you have any questions or need your car’s cooling system checked, please get in touch with us. 

Our Spa Motors team will be happy to look after you and your vehicle.

Today's engines have to perform at their best. Trimmed for efficiency, cleanliness and performance, and installed in tight engine compartments, the machines must operate continuously in an optimal temperature range. This is possible due to the liquid cooling system, which works in almost every car and motorcycle. Only with this, engine developers can realise such close manufacturing tolerances that are required for compliance with all limits. 

Before that time, engines did not need such complex cooling systems. The ambient air was enough to protect the engine from overheating. Large-area ribbing on the cylinders and cylinder heads resulted in an increased surface area and thus a release of heat to the environment. In narrow engine compartments, air baffles and fans support the airflow. 

How do I detect a defect in the cooling system of the engine? 

If there is a defect in the cooling system, this can result in two things. For one thing, the engine can overheat and cause severe damage. This happens when there is no or too little cooling water in the engine, or it cannot be moved to the radiator. You notice this by a sharp increase in engine temperature or by a corresponding warning light in the cockpit. If there is a sudden substantial loss of water while driving with white smoke coming from the engine compartment, it is the escaping water evaporating on the hot engine. 

Attention - leaking cooling water must be removed from the road surface as it is very slippery and can lead to accidents (not to forget the impact on the environment).  

A particular danger is a loss of cooling water "overnight" - If the engine is started without cooling water and the car has no warning if the water level is too low, a defect remains unknown. The water temperature gauge can only measure the water temperature. If there is no water, it will not show anything - another indication of a defect. 

Another possible defect is noticeable especially in winter when the engine does not come up to temperature. This results in increased consumption and increased environmental impact. This is triggered by a defective coolant thermostat. If your temperature gauge does not reach the 90-degree limit even after a long drive, this indicates a defect. Drivers of vehicles without display can recognise this by a significantly reduced heating power inside the car. 

Below we will introduce you to the components of the cooling system in more detail 

The water cooler 

The radiator belongs to the so-called "large cooling circuit", i.e. the part which is switched on only when reaching a specific cooling water temperature by means of a thermostat. The radiator is the component through which much of the heat from the cooling water is dissipated to the ambient air. For this purpose, the hot coolant is passed through a pipeline which is surrounded by fins, via which the heat is dissipated. The radiator is usually in the engine compartment at the front and is located between the two headlamps directly behind the radiator grille. 

The radiator is protected by the grille against coarse rock damage and other external influences. Nevertheless, rock fall may hit and damage the radiator. In addition, the cooling system is subject to high pressure, as the hot cooling water naturally expands. It may, therefore, be due to manufacturing errors that the radiator bulges and creates a so-called "blower cooler". To eliminate this, it already helps to replace the radiator cap. If a "Blow cooler" occurs, a leak due to an overload or rock fall is no longer far away and the cooling water comes out. In addition, the radiator can burst when the cooling water freezes. 

For smaller leaks in the radiator, the use of a radiator sealant helps, but in the long term, it is necessary to replace the radiator.  

The radiator fan 

The radiator fan, also belongs to the so-called "large cooling system". The fan is located in front of or behind the radiator and is switched on via the thermal switch when the temperature of the cooling water reaches a certain value. The radiator fan ensures that enough heat is dissipated, even when the car is stationary. 

If the needle of the coolant water gauge rises unsteadily in a traffic jam or during stop-and-go, it may be because the radiator fan does not switch on. There can be different reasons for this. So there may be a defect of the electric motor in the fan. This can easily be checked by bridging the thermal switch. If the fan does not make a sound, it is very likely due to the electric motor. If the engine starts, the thermal switch can be the cause of the problem. 

Attention: The radiator fan is a fast rotating part, it could cause injury. 

The water pump 

The water pump, also called coolant pump, has the task of keeping the coolant in circulation. The coolant pump is driven by the engine via the toothed or V-belt. In modern variants, the coolant pump is electrically driven, so that they can only be switched on when needed. The water pump was integrated directly into the engine block in older vehicle models, in newer models, they are housed outside the engine in a separate housing. Since the coolant pump is a flow pump that does not aspirate the fluid, the cooling system must be well vented for the pump to operate. 

The purely mechanical pumps are usually hardly prone to failure. Defective seals can lead to loss of cooling water and defective bearings lead to loud noises or complete failure of the water pump. Some manufacturers, therefore, require the replacement of the water pump at regular intervals. Electrically powered water pumps have the same main drawbacks, but there is sometimes an interface to the engine electronics, which registers the failure of the pump and outputs as a fault. 

The thermostat of the cooling system 

The thermostat is a valve that has the task of opening the cooling system for the "big cooling circuit" at a certain temperature. This happens mechanically in old vehicles, e.g. over a bi-metal strip, which expands at a certain temperature. Modern vehicles have electronic thermostats that open or close the cooling circuit according to the requirement profile of the engine management system. If the engine is started when cold, only the small cooling circuit is switched on when the thermostat is working, ie the cooling water does not flow out of the engine to cool down. In this way, the engine should reach the operating temperature faster. At optimum temperature, fuel is saved and emissions are reduced. When the engine reaches operating temperature, the thermostat opens the large cooling circuit. This happens at about 80 to 90 degrees Celsius. Now, the cooling water is cooled over the large circuit and kept at optimum operating temperature. 

The mechanical thermostat tends to fail due to stuck components. This can be determined in a very simple way. If the radiator and the radiator hoses of the large cooling circuit remain cold after a long drive, this is a sure sign that the thermostat is stuck, so that the condition of the small cooling circuit is permanently maintained. The thermostat must be replaced, otherwise, long-term damage to the engine may occur. If on the other hand, it takes a very long time until the engine reaches the operating temperature and the radiator and the radiator hoses of the large cooling circuit become warm from the beginning, the large cooling circuit is permanently open. Again, the thermostat should be changed immediately, as the fuel consumption and emissions increase. Electronic thermostats, like the water pumps of electronic design, have the advantage of transmitting interference to the electronics. 

Radiator Hoses, Expansion Tank & Co 

Of course, the cooling system as a complex unit still has other components which can suffer a defect. The radiator hoses are made of rubber and can become porous over time. This also leads to loss of coolant such as hose clamps that lose tension due to ageing or reservoirs that become porous or cracked. A look at all hoses and connections brings clarity here. Cooling water losses leave traces, mostly white or greenish deposits. 

If, despite all the search, there is no fault in the cooling system, there may be a defect in the engine. If the coolant was too low in antifreeze, the engine could freeze in winter. Corresponding frost plugs ensure that the engine block is not blown up, but expands specifically. These plugs work only once, so they need to be replaced when the cooling water is frozen. If the error does not occur here, the cylinder head gasket may be defective. This can be seen on a white exhaust cloud, or oil deposits in the cooling water. 

Our expert advice: The coolant in the cooling water not only has the task of protecting against frost, it should also protect the cooling circuit against corrosion. Regular replacement of cooling water is inexpensive and extends the life of all components.