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What to do if the cooling fan is constantly running: causes, solutions and recommendations
What to do if the cooling fan is constantly running: causes, solutions and recommendations

There are many important components in a car, and the quality of the car as a whole depends on how well they work. One of these is the cooling system. Often on some models it happens that the cooling fan is constantly running. This is not a very good sign. Insufficient cooling of the engine can lead to overheating of the motor - and this, in turn, can result in a large amount of money for the owner to overhaul. But if you know the reasons for such work in the cooling system, you can quickly identify where the malfunction is hidden and eliminate it. In order to find a breakdown, you do not need special knowledge and skills. Even a beginner can handle it. There are not many reasons why the cooling fan is constantly running.

The principle of operation of the fan in the cooling system

One of the reasons whythe fan can work constantly or turn on frequently, it is laid down in the principle of the system. The fan starts at the command of a special sensor. It is located on the bottom of the radiator. This sensor is responsible for the coolant temperature readings. If it is more than needed, then the radiator fan will start.

cooling fan constantly running

When its blades rotate, additional airflow is created. It helps to lower the temperature of the coolant, which will then pass through the channels in the engine. The cooling fan is constantly running only on motors that overheat for some reason. To avoid serious problems, it is necessary to respond to this problem immediately.


The engine may overheat due to the thermostat. It often happens that the mechanism of this element is jammed. The fan, in turn, necessarily reacts to this. The thermostat itself remains only half open.

cooling fan constantly running

As a result, the coolant cannot effectively remove heat from the engine, as its movement through the system slows down. When the power unit overheats and the coolant temperature rises, the sensor reacts to this event and starts the fan. Often, owners of Opel Astra cars face such a problem - the cooling fan is constantly running. And the problem is solved by replacing the thermostat.

How to check the thermostat of the cooling system

Testing it is pretty easy. For thisit is necessary to start the engine and warm it up to such temperatures when the valves of this mechanism will work. You can find out the temperature threshold directly on the device case. Usually it is 72 or 80 degrees. Then you need to check the temperature at the lower and upper nozzles. If both have approximately the same temperature, then the reason why the cooling fan is constantly running has been found. It is recommended to carefully inspect the thermostat valves after it has been dismantled. It is useless to repair this unit (it is easier and cheaper to buy a new one). By the way, if this element is dismantled, it can be checked without installation in the car. To do this, the thermostat is placed in a container with water, which is then heated. On the rise, the valve should open. If this does not happen, the device is out of order.

Cooling system pump

Sometimes the water pump is the reason why the cooling fan keeps running and won't turn off. The temperature of the coolant in the radiator rises because the speed of its movement is slowed down. When the liquid enters the cooling radiator, the antifreeze simply does not have time to cool to the desired temperatures and passes to the next round. This heats up the liquid even more.

Radiator cooling fan constantly running

When the pump works somehow, the fan can report a malfunction. If the pump is completely broken, then the engine will boil instantly - this usually begins serious problems and costly repairs.

Pump malfunctions

Often, the pump does not stop itswork all of a sudden. At first, the pump gives various breakdown signals - for example, the engine cooling fan is constantly running or turns on frequently.

The main cause of pump failure is considered to be the bearing - it jams or collapses. The fact that the pump is out of order can be understood by the characteristic sounds from under the hood. They look like a howl or a knock. These sounds can be heard even at idle. Novice motorists often do not pay attention to these noises. Pump knocks are taken for camshaft malfunctions. To fix the damage, you should replace the pump. Depending on the model, you can install only the front of the pump and replace the bearing.

Clogged cooling channels

Often the engine is overheated due to congestion in the cooling system. The situation is further complicated by the fact that diagnosing this problem can be quite difficult. Therefore, if the cooling fan is constantly running or turns on more often than usual, it will not be superfluous to flush the SOD channels. In most cases, these activities are more than enough to get everything working properly. Also, experts recommend not only flushing, but also additionally purge the radiator.

How to clean the cooling system

When cleaning the channels of the cooling system and radiator, the antifreeze is also replaced. To flush, the old antifreeze must be drained. Then a sufficiently strong solution based on citric acid is poured into the system. This is an effective folk remedy, but there are also various liquids with additives.

opel astra cooling fan constantly running

After that, start the engine - so the car should work for 30 minutes. This is enough to thoroughly clean all the channels. Then you can turn off the engine, drain the cleaning mixture, and finally fill in fresh antifreeze. Often in this way it is possible to completely solve problems in the operation of the cooling system, if the cause is contamination.

Clogged radiator

Car owners with experience know that the radiator is installed at the front of the car. When moving, it is blown by wind and air from the street. Also, it is the radiator that accounts for all the dirt and road dust. Poplar fluff, bird feathers and much more accumulate on the element. Over time, all this debris is clogged inside the plates, thereby reducing the efficiency of heat transfer. The oncoming air flow does not cool the antifreeze well. It heats up and the cooling fan runs constantly.

How to flush a radiator

To correct the situation and protect the motor from fatal overheating, it is recommended to clean the element. On most modern cars, you first need to dismantle the part, but often you can clean without dismantling.

engine cooling fan constantly running

Experts recommend cleaning with plain water. It is best if it is fed through a hose. Sometimes it makes sense to clean the radiator cells with a brush and only then flush. Often this procedure is combined with blowing out the radiator with compressed air.

Air locks in the systemcooling

For experienced car owners, air congestion is not a secret at all. They occur due to some errors in the process of replacing the coolant. Leaks in the system are also causes. Antifreeze cannot heat up evenly. This leads to instability in the operation of the fan. It often turns on or even works without interruption - hot coolant enters the radiator. Before trying to eliminate these same plugs, it is necessary to check the system for leaks. If they are found, then they should be eliminated. Next, you need to remove the plugs. This requires a compressor. One tube is unscrewed from the throttle, which supplies fluid. Then a compressor is connected to the neck of the expansion tank and the air supply begins. Two or three minutes will be enough to clear all traffic jams.

Temperature sensor problems

If the cooling fan on the VAZ 2107 is constantly running, then the radiator temperature sensor on both carburetor and injection cars is often to blame. In most cases, it is simply closed.

the cooling fan is constantly running

If the symptoms are exactly like this, then check the time for which the fan turns on, and compare the temperature when it is turned on with the standard one. If the readings are lower, then the problem is easily solved by replacing the sensor.

Insulation for the winter period

Many motorists try to insulate the radiator during the winter - there is an opinion that this way the engine will warm up faster and save moneyfuel. However, during thaws the air temperature rises. If a heater is installed, the engine will not be able to cool effectively. This may be the answer to the question of why the radiator cooling fan is constantly running. But this is a rather rare reason.


So, among the most popular reasons why the fan is unstable, one can single out problems with electronics. This is what most car owners complain about on specialized forums. Many solve this malfunction by replacing the sensor and fuses. And it helps. In half the cases, the issue can be resolved by replacing the thermostat. Also, the situation can be improved by cleaning the radiator.

why does the cooling fan keep running

Problems happen on any car, this topic worries Ford Focus car owners. The cooling fan is constantly running on luxury cars. It is important to notice this problem in time, otherwise it can lead to disastrous consequences. In case of severe overheating, only a major overhaul with the replacement of the cylinder head, cylinders, pistons and other components can help the engine.

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