How To Top Up Your Car Coolant

Coolant is responsible for maintaining the proper temperature of the car's engine. It is recommended to check the coolant level once every 1000–2000 km. Check out how to add coolant and how to do it safely. We also explain how to change the coolant in your car.


What does the coolant do in a car?

Coolant is one of the most important fluids in a car. It has certain chemical properties and circulates through the cooling system. The function of the coolant and the cooling system is to maintain the optimal temperature of the engine and dissipate the heat generated during its operation.

The ignition of fuel in the engine runs most efficiently in a certain, well-defined temperature range. At too low a temperature, fuel liquefaction occurs, and at too high a temperature, knocking combustion or premature ignition (in diesel engines) can occur. Temperature also affects the dimensions of engine components, which are designed to operate within the operating temperature range. Automotive parts under the influence of temperature can change their volume.

In older cars, optimal operating conditions for the engine are achieved when the coolant temperature is between 85 and 95 degrees C. In the newest cars, the operating temperature reaches up to 115 degrees C.


What is engine coolant made of?

Automotive engine coolant consists of:

- 50% demineralized water;

- 49% ethylene glycol;

- 1% chemical additives (anti-corrosion and decalcification)

Coolant concentrate is usually mainly glycol and additives, and contains minimal amounts of water. The composition of coolants varies depending on the climate zone in which they are to be used. In Europe, off-the-shelf coolants are used, which most often consist of 50% demineralized water, 49% ethylene glycol (polyhydroxy alcohol) or propylene glycol, and less than 1% additives.


How often should I replace coolant?

Coolant wears out and loses its protective (e.g., anti-corrosive) properties. The fluid can also get contaminants from the cooling system (corrosion, scale, etc.) or, in the worst case, engine oil. Alcohol in the fluid evaporates faster than water, so its concentration decreases over time, which affects the properties of the substance. The coolant in the car should be replaced according to the manufacturer's recommendations in the owner's manual, or:

- universal fluids: the frequency of fluid replacement is 4 years;

- branded concentrates or from the car manufacturer - the correct fluid replacement should be done every 6 years;

- It is important to change the fluid when the coolant is contaminated;

- for any repair that requires you to drain the coolant.


Information about the recommended service life of a particular product should be on the fluid label.

It is also a good idea to replace the coolant after buying a used vehicle, for example, one from the last sold cars list. Replacement can be done along with the regular replacement of the timing and water pump, but in some cars, this is not required (older engines with chain timing). In this case, the coolant should be replaced at the first repair or immediately after buying a used car.

Worn fluid may contain contaminants from the poor condition of the cooling system (when it rusts) or, in the worst case, engine oil. In this case, the cylinder head gasket may be damaged. The fluid requires regular inspection. Manufacturers recommend that at least once a year (preferably before winter), you do a special test that checks at what temperature the fluid will freeze. Coolant should be added when the fluid level in the expansion tank is below the minimum value. Regular coolant replacement is necessary, as is flushing the system every few years.


How do you top up your engine coolant?

The most important thing to remember when topping up the coolant is to do it on a cold engine. A warmed-up system has increased pressure. Therefore, unscrewing the reservoir will cause the fluid to shoot outward. This can risk burns. Using cold fluid is the basic rule for all service work with coolant in the cooling system.

There are minimum and maximum level markings on the wall of the expansion tank. Add the appropriate amount of coolant to the maximum level, close the cap and run the engine for a few minutes. When the level is below the maximum level after turning off the engine, you should refill it again.


How to change engine coolant?

If you want to replace the coolant yourself, prepare a container for used coolant (after such an operation, it must be returned to a waste collection point). When changing the fluid, use the protective measures recommended by the coolant manufacturer.

If you are replacing the coolant, you need to drain the fluid in the radiator and throughout the system. Most cars have a drain plug. Stand a large bowl or other container under the car and unscrew such a plug. When the cooling system is drained, replace the cap and pour the new fluid into the expansion tank to the maximum level.

To properly replace the coolant, it will be necessary to bleed the system. Unscrew the valve designed for this purpose and start the engine. To check whether the system is bleeding, you can turn on the heater. If it works effectively, there should be no air in the fluid circuit.

Read also:

What are signs of a bad starter? How to fix it?


Is it ok to use water as coolant?

To keep the cooling system in good condition, follow a few basic rules. First, water should not be used in the cooling system instead of fluid, especially straight from the tap. This risks scaling the system and damaging its components. Secondly, frequent replacement of the coolant and the use of quality products will avoid numerous failures and prolong the life of the drive unit. Follow the manufacturer's recommendations or use high-quality replacements.

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