All you need to know about coolant

06 January 2022, 10:15

Keeping tabs on your coolant is an important part of owning a car. The coolant ensures that the car's engine does not overheat, and that the cooling system does not freeze in winter. But what exactly is coolant – and how do you make sure your car always has enough?

In this post, you can read everything you need to know about coolant. Find out how to top up coolant, which coolant to choose and what to do if your car is using more coolant than it should.

What is coolant – and how does it work?

Coolant is often water mixed with glycol to lower its freezing point. This ensures that the car's cooling system doesn't freeze up in winter. The fluid also contains a dye and various additives that lubricate the engine parts and reduce the risk of rust and corrosion in the radiator.

Coolant is used by the car's radiator to cool down the engine so it doesn't overheat. The cooler is a radiator with a thermostatic valve that records the temperature of the car. When the engine reaches a certain temperature, the radiator sends coolant into the engine to cool it down.

The coolant then returns to the radiator, which cools the liquid. Cooling is achieved, among other things, by the air flow that occurs when the car is at speed.

Red or blue coolant – what's the difference?

The dyes added to the coolant indicate which type of engine the coolant is intended for: cast iron or aluminium. The two types of engine need different additives.

As a rule, blue coolant is for cast iron engines, while red is for aluminium engines. A good rule of thumb is that if your car is from before 2000, you should choose blue coolant. If your car is from after 2000, choose red coolant.

How to add coolant to your car

When filling your car with coolant, first make sure you mix coolant and water (preferably demineralised). It is a good idea to mix the liquid in a container before filling.

Before adding the coolant, make sure the car has cooled down. If the car is hot, the cooling system is pressurised, which means the coolant reservoir may be expanded. This means you will not be able to see how much liquid to put in the reservoir.

If you open the reservoir while the engine is still hot, you also risk getting burned when you release the pressure. That's why you should always let your car cool before adding coolant.

Once the car has cooled, follow these steps to top up the coolant:

  • Find the cap with the thermometer icon in the car's engine compartment. If you're not sure which cap is the right one, check your car's owner's manual.
  • Carefully unscrew the cap to slowly release any pressure.
  • Locate the mark on the reservoir indicating maximum fill, and top up with coolant until the mark is reached. Don't top up beyond the mark, as there must be room for pressure in the reservoir when the car heats up again.

What does it mean if the car uses more coolant than normal?

If your car is using more coolant than it should, it could be due to a leaking head gasket. If you suspect there's a problem with your car's head gasket, you should get it fixed as soon as possible. Otherwise, you could end up with very expensive repairs. Find repair quotes here.

Remember to change the coolant once a year

The additives in the coolant degrade over time. This means that, although they prevent rust and corrosion in the radiator, over time they can expose the radiator to corrosion as the additives degrade.

That's why it's a good idea to change your car's coolant once a year, so you make sure the additives in the fluid are working as intended.

You can replace the coolant yourself. However, we recommend that you leave it to your garage. This reduces the risk of contamination: Under no circumstances should coolant be poured down the drain or into the ground.

Have the coolant changed during servicing

During a car service, consumables are checked and the mechanic also checks the coolant. If the coolant needs changing, the service is a good time to get it done.

With Autobutler, you can compare prices for servicing at the country's leading garages. That way, you can save money on your next car service and have it done at the garage that suits you best. Follow our other satisfied customers' recommendations and use Autobutler to compare service quotes.

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