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Why Low Coolant Light Comes On And Off?

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You were driving your car in a clear, relaxed atmosphere to your destination, calmly and soothingly. Suddenly you observe that the low coolant light comes on and off in your vehicle. And after analysing the situation, you come across a defect either in your cooling system or your coolant light.

I know all this will ruin your mood and invite a new problem to the vehicle. Therefore, first of know the exact reason behind the fault in the coolant light and then work on it.

As coolant light plays an essential role in maintaining the vehicle’s temperature, it must function properly to avoid issues related to the cooling system. Here, our article provides you with the basic knowledge you may apply if you are stuck in such situations. So, let’s begin with the discussion on the topic.

What Is A Coolant In a Car?

A coolant is a mixture of water along with the chemicals manufactured to prevent corrosion inside the engine. A cooling system maintains the ideal temperature in the vehicle while driving using a thermostat. The thermostat is appointed to restrict coolant flow when the engine is cold to achieve an efficient working temperature quickly.

Car coolant is also known as antifreeze as it protects the vehicle’s engine from overheating. It also lubricates the various parts which come in contact with it while performing its function. The lubrication helps to protect the water pump, head gasket, cylinder and piston of the vehicle.

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The coolant is responsible for pulling the heat away from the engine. So, we cannot drive the car with a faulty cooling system as this would overheat the engine. And continued use of an overheated engine may permanently damage the other parts of the engine, like the piston welding to the cylinder.

Why Low Coolant Light Comes On And Off?

The coolant light will come on when the sensors connected to it observe some incorrect changes in the temperature and the coolant system in the vehicle. Generally, the coolant system adjusts the varying temperature requirements of the car.

When the low coolant light observed on the dashboard, the first thing is checking or inspecting the coolant levels. If that is not the reason, the following reasons listed below is one of the causes.

1. Sensor Malfunctioning

It is the most common case when your coolant light switches on and off without any definite reason. The failure in sensors of the coolant system generally observed in vehicles. A bad coolant sensor may decrease fuel efficiency or cause your car to fail emission inspection, which is a significant concern for the car.

The most likely reasons behind the faulty sensor are the loose or corroded connections and not the actual fault in the sensor. So, check all the contacts related to the sensor thoroughly.

And if you see any cracks, badly corroded parts, or your sensor is pretty old, then the repair or replacement is the best option. For this, visit your mechanic and get it done as soon as possible.

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2. Coolant Leaks

A coolant is responsible for maintaining the temperature of the vehicle with adequate pressure. Generally, it meant for the cooling system to keep the car cool. The leakage in the coolant not only malfunction our sensor lights but also deteriorate the car’s efficiency.

There could be multiple varieties of reasons for coolant leaks, and some are easy to handle while others damage the vehicle to a greater extent. However, the causes are a leaky radiator cap (when the coolant eliminates the overflowing tube due to car heat-up).

Another reason could be the leaky gasket due to the exemption of coolant from the system. And the third reason for leaky coolant is the physical puncture in the radiator cap of the vehicle. Analysing the physical punch is the easiest of all the reasons.

Thus, knowing the exact reason behind the faulty sensor lights is quite tricky; therefore, checking the coolant leaks will help you out in these cases.

3. Faulty Thermostat

Some sensor problems originate from the thermostat of your vehicle rather than the sensor itself. The thermostat is the device that regulates the temperature level in the car, and its failure is again a matter of concern.

These conditions, such as the thermostat stuck open, can cause a decrease in the vehicle’s temperature and consequently result in sensor defects. There are also the conditions where the thermostat stuck in the closed position will prevent the flow of coolant, and thus the vehicle’s engine is overheating.

All these reasons are responsible for low coolant light switching on and off without any reason. In such situations, you only need to repair your thermostat. And if you have recently replaced your thermostat, check to see that it replaced with the correct temperature range.

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4. Cold Or Changing Weather

Whenever you park or keep your car in cold or freezing temperatures, the coolant in the cooling system contract; thus, it causes a defect in the coolant sensors. And all this signifying the low coolant level in the vehicle due to the lightning up of the coolant.

These situations occur very frequently in countries with low temperatures or rapid weather changes. Therefore, people living in the cold especially take care of such cases.

While dealing with the problem, you only have to check your coolant level and top it off with any other coolant to attain its original volume. The procedure can do either by yourself or by visiting a mechanic. And also, please choose the best top it off for your vehicle to avoid further uneven conditions.

How Much It Cost To Fix The Low Coolant Level In Car?

The average cost of fixing the low coolant level in a car is pretty expensive. After all, it prevents the overheating of the engine and other important functions. The cost may range between $350 to $500. However, it may vary depending on the vehicle and the place.


We hope all the readers got their well-explained answers. So, now whenever your low coolant light comes on and off, first diagnose the cause and then act accordingly to get the solution. Thus, it would not only help you but save your vehicle from severe damage.

If your doubts and queries regarding the topic persist, comment below in the comment section. Soon we’ll answer all your questions as quickly as possible.