What exactly is a cooling circuit?


A cooling circuit is a vehicle’s mechanism designed to keep all thermally-stressed areas of the engine from being damaged. The internal combustion necessary for powering vehicles produces substantial heat, and the coolant circulating in the cooling circuit dissipates this heat to ensure a constant engine temperature level in the engine.

The main function of a cooling circuit is to ensure that the engine runs at its optimal operating temperature. While extreme high temperatures can cause overheating, seize, and cracked engine blocks, a cold engine can result in worn out components, more pollutant emitted and a less efficient engine.


Cooling circuit components

The cooling circuit’s main core component is the water pump; in charge of activating the circulation of the coolant through the entire circuit. Other key components include the radiator; in charge of transferring the heat from the fluid inside to the air outside, and the thermostat; which ensures that the liquid is at the right temperature by blocking or opening the passage.

Together with the previously mentioned elements, other components such as freeze plugs, cooling fans, head gaskets, hoses and an overflow tank amongst many others, all add up to keeping the temperature within standards of safety and efficiently.


Related content: Engine cooling system: how it works and main components


Cooling system: main problems


Cooling systems fail more often than any other mechanical system, usually related to poor maintenance and neglect, or in relation to external wear causes. The following are some of the main causes of cooling system problems.


Poor use of liquid coolant

Cooling system designers have formulated complex mixtures of water and waterless mixtures with various additives that reduce the freezing point of coolants and prevent corrosion of the metals involved. 

However, specific coolants are suitable for different vehicle models and misdoings such as not using the coolant mixture specified in the vehicle’s manual and/or low coolant levels will negatively affect the water pump and engine temperature.


Failures in auxiliary equipment

Another of the most common cooling circuit problems involves failures in auxiliary equipment. The misfunctioning of closely involved components such as the thermostat or the radiator cooling fan will destabilize engine temperature

The thermostat, for instance, helps an engine identify when it needs to cool down. But if it is failing to work properly, the engine will continue to get hotter and hotter until the damage is irreversible. Another example is the radiator cooling fan; if this component breaks down, heat will not be able to dissipate from the coolant, and this will result in overheating and potential engine damage. 


Pressure drops

When pressure within the system drops or is not evenly distributed throughout the cooling circuit, vibration is subject to cavitation (vapor formation). 

If this happens while the engine remains under load, metal temperature will spike and the hot spots will cause important issues such as pump flow interruption, erosion damage, poor engine efficiency, detonation, power loss and full-blown overheating.


Diagnosis related to the car cooling.


This post addresses some of the most common cooling circuit issues, while providing insights into how to address and prevent these. A poor or incorrect use of liquid coolant is one of the main issues causing cooling circuit problems. 


Loss of liquid coolant due to leakage

Even though leaks in the cooling system can be easy ailments to diagnose, they are certainly harder to locate. Signals of a coolant leak include the temperature gauge pointing towards the red zone, steam coming from under the hood or the engine facing a sudden stall.

There are three main causes for coolant leaks: external leaks, radiator cap leaks and internal leaks. Whereas external leaks can be noted by basic inspection, internal leaks are usually caused by faulty components. Whichever the case, identifying, sealing and repairing involved components is a must, and cleaning any resulting contamination should come with it.



Probably the most common symptom of a cooling system failure, overheating of vehicle’s internal parts can result in a variety of distressing effects; from burned valves, to damage of the cylinder head gasket and engine seizure. 

It is usually caused by an insufficient quantity of liquid in the circuit, but the truth is that the causes for overheating can be multiple. What is most important is the fact that any indication of overheating will deteriorate a vehicle, so shutting down the engine and fixing the problem is the best practice to prevent further damage.


Frozen coolant and overcooling

If the engine and other inner vehicle parts are running below the normal operating range, the engine will lack achieving full; consuming more fuel and therefore meaning more pollution. This matter will also increase cylinder and other component wear due to the increased amount of fluid friction loss. 

This is usually due to extreme temperatures affecting the coolant temperature, especially when the thermostat opens too soon or the valve remains open for too long. If the vehicle stands still for a long time where the ambience temperature is below the freezing point, the coolant may freeze completely and may cause serious breakage to any part of the system.


Incorrect temperature gauge reading

Sometimes, it is not the actual cooling system what is failing, but the temperature reading. When the engine is functioning, and the coolant is doing its job, the temperature gauge needle should be somewhere in the middle between the hot and cold indicators.

Temperature sensors can also fail, so if the indicator fitted on the instrument panel is signaling tricky readings, a thorough check should be carried out to measure real cooling temperature and contrast it with the reading of the gauge.


Keep reading: The importance of using the right coolant liquid


Other factors and concerns to consider


While the list of causes, signals and issues related to cooling circuit problems might seem never-ending, the truth is that with correct observation and preventive maintenance, the cooling circuit can have a long operating life.

It is a matter of attention, care and common sense. For instance, sudden noises in the cooling system are an evident signal that something goes wrong, and the same happens with most of the factors listed above. 

With regard to the correct use of coolant, a simple look into the cooling circuit will let you know whether it has been maintained correctly. By looking inside the expansion tank, the pipes, and the water pump, you can look out for clear signals such as the appearance of solid residues, yellowish and reddish coloring, white spots and incrustations, as just a few examples, that indicate the use of an unsuitable coolant.


Dolz, leader in the manufacture of water pumps for the aftermarket.


In addition to the water pumps, it also has a wide range of thermostats, thus completing its range of cooling products for the vehicle.

Contact us to learn more about our range of water pumps and products!


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