Coolant, sometimes called antifreeze, keeps your engine at a safe operating temperature all year round and stops the system freezing in winter. A low coolant level is one of the most common causes of a car overheating, and it's also one of the easiest things to check and top up yourself.
Checking the level safely
Coolant is held in a plastic expansion tank under the bonnet, marked with minimum and maximum lines. Only ever check or open this tank when the engine is cold. The system is pressurised when hot, and opening it can release scalding coolant and steam. If the car has been running, leave it for at least half an hour before you go anywhere near the cap.
Topping up correctly
Once the engine is cold, check the level against the markings on the side of the tank. If it's below the minimum line, top up with a coolant mixture that matches the type already in the system — check your handbook for the correct specification, as mixing different types can cause problems. Add a little at a time until the level sits between the two marks, then refit the cap securely.
Signs something isn't right
If you find yourself topping up often, that's a sign of a leak rather than normal use, since a sealed cooling system shouldn't lose coolant on its own. Look for green, pink or orange staining under the car, around hose joints, or near the radiator. A rising temperature gauge, sweet-smelling steam, or the heater blowing cold when it should be warm are all worth investigating promptly with a garage.
A quick seasonal check
Before winter, it's worth confirming the coolant will protect against the temperatures you're likely to face, since a weak mixture can freeze and crack the engine block. Many garages will check this for you quickly and inexpensively as part of a general once-over.
Keeping an eye on coolant costs nothing and takes moments, but an overheated engine can mean a very expensive repair. Make it part of the same routine as checking your oil.
