Engine Coolant – What is it and how to check

Engine coolant helps keep your engine running efficiently and helps prevent it from overheating, and so it is crucial to ensure your vehicle has enough coolant, read on to find out more.

Our comprehensive guide will help you identify any potential issues, how often you should check it and clarify how you can keep your engine coolant in an optimal condition.

What is engine coolant in a car?

Engine coolant is a liquid that helps to keep the engine of a car cool, it is also known as antifreeze. Typically it is a solution made up of water and antifreeze and circulates through the engine to protect the engine from overheating. It also helps protect the cooling system from freezing up in the extreme cold.

The coolant circulates through your engine, absorbing heat from the engine. It then flows through the radiator where it is cooled by the air flowing through the radiator.

Over time the coolant can evaporate out of the system, sometimes the level can drop so much that new coolant will need to be added to the system. Often only a top-up is required, to substitute any fluid that has evaporated out of the system. Sometimes though, a full coolant change is needed if it is no longer in a good shape.

What is the difference between antifreeze and coolant?

Antifreeze and coolant are related but different. Antifreeze is an ethylene glycol-based liquid, and it is mixed with water to make up what is known as coolant. So whilst the terms coolant and antifreeze are often used interchangeably they’re not quite the same.

Antifreeze does not boil or freeze easily hence it is used as part of coolant to help maintain the engine’s ideal operating temperature. In car shops you will find pre-mixed engine coolant, containing a mixture of antifreeze and water, as well as undiluted antifreeze to mix with water yourself. It is recommended to check your car’s owner’s manual to see what type of coolant mixture your vehicle needs.

How often should you change engine coolant?

This differs from vehicle to vehicle. In general, it is recommended that the coolant is fully refreshed at least every 5 years, if not sooner. Some newer car models may require coolant servicing every 10,000 miles.

It is important to change your engine coolant periodically because it helps maintain engine efficiency and prevents your engine from overheating. Over time, the coolant can become contaminated and gets deteriorated and needs to be replaced.

Your vehicle handbook will have detailed information about when you need to change your engine coolant, and it is recommended to follow the advice given to help keep your engine in a good condition. If you’re unsure about how to change your engine coolant then a professional mechanic on ClickMechanic can help.

How to check your coolant or antifreeze?

Car engine bay with coolant reservoir

To check the coolant level, in modern cars you can check the level on the coolant reservoir, usually one of the see-through tanks under the bonnet next to the engine. Make sure your vehicle is on a level surface. Your coolant should not drop below the minimum line, nor go over the maximum line. If it is below the recommended level then make sure to top up the coolant. Check the vehicle handbook for the coolant reservoir position and recommended procedure.

How to replace coolant or antifreeze?

To change the coolant or antifreeze in your car fully, you will need to drain the old coolant from the cooling system and refill it with new coolant. In some cases, you will also need to flush the cooling system to remove any debris or contaminants.

Normally the procedure to replace your coolant / antifreeze will include the following, but may vary by manufacturer:

  1. Make sure the engine is cold and if recommended is raised safely off the ground according to manufacturer guidelines
  2. Drain the coolant from the system, usually by undoing the drain valve or the bottom radiator hose
  3. If needed, flush the coolant system until clean. Mechanics would usually do this with high-pressure water
  4. Refit the drain valve or the radiator hose to secure the cooling system. Then refill the system with the correct engine coolant mixture for your vehicle and follow the instructions in your vehicle handbook
  5. When the cooling system has been refilled according to manufacturer guidelines bring the engine back to operating temperature and ensure any air is removed from the system
  6. Make sure that there are no leaks anywhere in the system and that the cooling fan works as expected

Remember, if you’re not sure how to do this, it’s always better to have a professional mechanic do this for you. The procedure required will depend on your vehicle and may be different to the procedure above.

ClickMechanic offers assistance if you have never topped up or changed antifreeze or if you are unsure how to do it.

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What coolant does my car need?

The correct coolant / antifreeze mixture for your car will depend on the make and model of your vehicle. You can typically find this information in your car’s owner’s manual. Keep in mind that using the wrong engine coolant will likely cause irreversible damage to your car’s engine and cooling system.

For most cars a regular coolant and antifreeze mixture will normally be good enough. Different mixtures are available and can be identified by their colour. There are, for example, blue, red and green versions which all have different freezing and boiling points.

Multiple types of antifreeze are available, with each using a different type of corrosion inhibitor. There are three main types of coolant that car companies use: Inorganic Additive Technology (IAT), Organic Acid Technology (OAT), and Hybrid Organic Acid Technology (HOAT)

Can you top up coolant with water?

You should only ever top up your coolant with water if you have no other option, for example in case of an emergency when the coolant level has dropped below the minimum and you do not have the right coolant mixture to hand.

It should generally help to get you home or to a garage safely, you however shouldn’t continue driving like this. Make sure you replace the coolant with the recommended coolant mixture for your vehicle. Driving without the right mixture will mean that the coolant will be less efficient and you risk damage to your engine.

How much does it cost to change engine coolant?

It costs an average of £65 to change engine coolant, with prices ranging from £40 to £90. Ultimately, the cost of replacing engine coolant depends on your car and what parts are recommended by its manufacturer. Get an exact price for your vehicle make and model here.

How much does a coolant leak repair cost?

The cost of an engine coolant leak repair will vary depending on the make and model of the vehicle, as well as the severity of the problem. However, it is generally advisable to budget for at least £200 for a engine coolant leak repair. To get a better idea of the exact price for your vehicle type, enter your vehicle registration number and postcode on ClickMechanic to get an exact price.

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How to prevent your car from overheating?

There are a few things you can do to stop your car from overheating:

  1. Make sure that you have the correct amount of coolant in your car
  2. Ensure that the coolant / antifreeze mixture is as per the car manufacturer’s recommendation
  3. Check the cooling fan – a seized cooling fan is a common cause of overheating
  4. Check your car’s cooling system and make sure it is clean and free of debris
  5. Check your car’s thermostat and make sure it is working properly
  6. Finally, if you cannot find the cause of overheating, make sure to get a professional mechanic to check the vehicle. Driving a car that overheats can cause severe damage to your engine.

You can get a trusted mechanic booked online within one minute with ClickMechanic, book here.