How to Check Engine Coolant Levels

A water-based liquid that includes antifreeze, engine coolant is essential to regulating the temperature of your vehicle. If the level is low, you could be at risk of overheating your engine. This handy how-to guide offers step-by-step tips on how to regularly check and top up your engine coolant when it's low.

By Gumtree Editorial Team

18 February 2021 3 min read

1. Check your handbook

Look in your manufacturer’s handbook to check the location of the engine coolant expansion tank. This will normally be near the engine and above the radiator. Check the manufacturer’s instructions to make sure you buy the right sort of coolant.

The three main types of coolant are:

Inorganic Additive Technology (IAT) – this is mainly used in older vehicles and is green in colour, lasting around two years
Organic Acid Technology (OAT) – this is a newer formula mix of coolant and can be changed in five-year intervals or every 50,000 miles
Hybrid Organic Aid Technology (HOAT) – this is a derivative of OAT and requires changing every five years

2. Make sure your engine is cold

Leave your car for several hours after use or ideally overnight before checking the engine coolant. This is very important, as the expansion tank is pressurised and you could put yourself at risk of scolding if you attempt to unscrew the cap while the engine is still warm. A cold engine will also allow you to get an accurate reading of the coolant level.

3. Check the coolant level

You should see the minimum and maximum level marks on the side of the tank. The expansion tank is often a white plastic enclosure, so you should be able to carry out a visual check of the level of coolant in the tank using the level lines. If the coolant level is below the minimum line, then your engine could be at risk of overheating.

4. Top up coolant if it’s below the minimum level

Unscrew the cap to the coolant tank if the level of liquid appears lower than the minimum line. Take care when unscrewing the cap, as this may be pressurised. Fill the coolant to just below the maximum line – be careful not to overfill, as the liquid will need room to expand when the engine is in use. Once you’re done, screw the coolant tank cap back on firmly.

5. Check your engine coolant regularly

You should check your engine coolant levels at least twice a year – in the summer and winter – and top it up as required. You can also look for signs of a possible coolant leak by taking a look at the connected hoses. Wet or white stained marks could be an indication of a leak. If you think there’s a problem with your engine coolant system, get it checked out by a reliable mechanic.

To maintain the smooth running of your vehicle and prevent overheating, you should check your engine coolant levels regularly – at least twice a year. If the levels are low, topping up your coolant is a simple process that can be easily done at home. If you’re having to top up too regularly, it’s worth heading to a reliable garage to have the coolant system checked out.

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