Car Radiators: What Are They and How to Maintain Them

A car’s engine continuously heats up while in use, and if it becomes close to a dangerously high temperature there is a risk of a sudden explosion. Therefore, it is necessary to cool it down to a suitable temperature such as between 80 and 100 degrees Celsius, and this is where the radiator comes into play—it helps to cool down the engine to an appropriate temperature. Most modern engines are water-cooled in general, except some are air-cooled or electric cars such as with the Nissan Leaf. Here, we break down the components of a water-cooled engine radiator as well as how to maintain it.

Water-cooled Engine Radiator Components

A water-cooled engine has a coolant made of water in the water jacket around a cylinder, and it circulates to prevent the engine from overheating. A radiator is placed in the middle between the water pump outlet and inlet so that the performance of it is optimized. The whole route consists of the radiator, radiator hose, water pump, thermostat, and cooling fan. A lot of narrow passages for a coolant flow through the main body of radiator, which are called cores.
The purpose is to enhance the cooling effect by increasing the area of water passing through each core. The radiator itself merely doesn’t work—let’s have a look at each component of the radiator-related parts so that we can clearly understand each role. In combination with these parts, the purpose of radiator is fulfilled.

Cooling Fan

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While running, the engine’s temperature is lowered with fresh air, but cooling only by air is insufficient for  times such as during traffic jams in which the engine is not in motion and still generating heat. Therefore, the necessity of a cooling fan arises. It increases the quantity of air flow in front of the radiator, and enhances the cooling efficiency to a satisfactory level.

Water Pump

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The water pump circulates coolant liquid in the water jackets around the engine, the radiator itself, and its sub-tank so that the cooled coolant in the radiator runs back to the water jackets smoothly.


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The thermostat helps to keep the coolant stay within a fixed temperature of a designated range. It also stops the water flow to prevent coolants from circulating within the radiator in cases such as severe cold weather. When an engine gets heat-up, its water temperature accordingly increases, and it opens a water outlet fully when the temperature of coolant becomes approximately above 80 degrees Celsius, allowing the coolant liquid to circulate.

Radiator Cap

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Above: A car’s radiator cap

The temperature of the coolant can sometimes rise to 120 degrees Celsius. A pressure valve and a vacuum valve are located in the radiator cap respectively, and when pressure goes up due to the expansion of coolant liquid the pressure valve opens and moves an amount of coolant liquid flowing into the radiator into the reservation tank. When the pressure decreases, the vacuum valve opens and returns the coolant liquid into the radiator. In addition, it suppresses the boiling of the coolant liquid by keeping it at a constant pressure.

How to Maintain a Radiator

1. Check the Coolant Often

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Above: Examples of car coolants

When the water level of the coolant decreases and gets dirty with rust and water scale, it mostly causes overheating of the engine. We recommend to change the coolant liquid every two years. When rust and water scale are in bad condition, let’s wash them out with a radiator cleaner.

2. Check the Fan Belt

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Above: Example of a car’s radiator fan belt

The tension of a fan belt which moves a cooling fan can be checked by hand. Push the middle of the fan belt using your thumb, and if it can be pushed down to between 13-20mm, it means that the current tension of the belt is OK. When it is damaged to the extent that the rubber part melts and slips, the turn cycle of the fan is jeopardized which can lead to overheating and should be replaced.

3. Check the Radiator Hose

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Any cracks, slacks, or distortion of the radiator hose can cause water leakage, so it is recommended to regularly check the condition of the hose in order to prevent any unnecessary incidents.

What to Do When Your Car Overheats

If your car overheats, immediately find a safe place to pull over as soon as possible. Carefully open the bonnet, and keep an eye on the entire engine until you can visibly see that the water temperature has begun to fall. Never open the radiator cap, because there is a risk of high temperature steam shooting out and causing severe injury. If you can see that the amount of coolant is low, fill it to the designated level when the engine has cooled down.

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For this purpose, it is also recommended to always carry a dispenser of water in your vehicle in case of overheating emergencies. If the coolant seems to be at an adequate level, the cause of overheating may be due to damage to the water pump due to its crucial role in circulating the coolant liquid as previously mentioned.

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