I was looking under the bonnet of my car and noticed the coolant was below the minimum level. How do I top up coolant?

top up coolant

Topping up a car’s coolant is an important job. But it’s also a relatively simple one that anyone with even the scantest knowledge of how a car works can undertake. Read on to find out how to go about it.

Buy the right coolant

Coolant is a mixture of distilled (purified) water and anti-freeze. Confusingly, there are various types of it, named after the additives used in them to inhibit corrosion. You don’t need to know the various types. But you do need to get the right one for your car.

You can either buy ready-mixed coolant or concentrate. If you buy the latter you will also need some distilled water to mix it with. Ready mixed is easier because you can just use the amount you need and then store it in case you need it in the future.

You will find the type of anti freeze your car needs in its user manual. Alternatively, go to a website such as EuroCarParts which will explain what’s suitable for your car. Or you could go to the website of a coolant manufacturer such as Total.

top up coolant
Of all the fluids, anti freeze is one of the most important

Find the coolant reservoir

As our reader knows their coolant is low, they’ve plainly found the reservoir. If you haven’t, open the bonnet. You’re looking for a plastic bottle, probably with a pink or blue liquid in it. There’ll probably be an icon like a comedy blast of steam on it. And it’ll have min and max markers.

Don’t touch it if it’s hot

You want to do this job when the engine is cold. If it’s hot, releasing the lid of the coolant bottle could potentially unleash a blast of scolding steam.

If it is cold, top it up.

Assuming the engine is cold, unscrew the lid of the coolant reservoir. It’s best to cover it with a cloth, just in case. If there is any pressure in the system it will leak out. Anti-freeze is toxic so you don’t want to spill it if you can help it.

We advise using a funnel to put the coolant in so insert this into the open reservoir. Then look for the minimum and maximum markers on the reservoir. We’d top it up until the level is just below the maximum marker. To ensure you don’t overfill it, squat down so your eyeline is level with the reservoir.

Lastly, screw the cap back on until you hear a click. And that should be that.

Why does it need topping up?

One question you should ask is why does it need topping up. A car’s coolant system is a sealed unit. It shouldn’t leak but it can do so from hoses or the radiator. Giveaways are an over-active car temperature gauge and a sweet smell of the coolant leaking into the engine bay.

If you think your coolant system has a leak, you should take your car to the garage and ask them to inspect the system. If an engine is persistently running too hot, it can lead to permanent (and expensive) damage.