What is a Coolant Level Check?
Spot a leak early and you could save thousands on engine repairs.
Simplified animation — not to scale.
In plain English
Coolant (also called antifreeze) is the brightly coloured liquid — usually pink, red, blue or green — that circulates through your engine to carry heat away to the radiator. The expansion tank is a translucent plastic bottle in the engine bay with MIN and MAX markings on the side. The level there should always sit between the two when the engine is cold.
"Think of coolant like the sweat your engine relies on to stop overheating — run out and it cooks itself."
How it works
CRITICAL: only ever open the coolant cap when the engine is stone cold. Hot coolant is under pressure and can erupt and cause serious scalding. With a cold engine, simply look at the side of the translucent expansion tank — you should see coloured liquid between MIN and MAX. If it's low, unscrew the cap slowly and top up with the correct coolant for your car (check the handbook — using the wrong type can cause corrosion). Pre-mixed 50/50 coolant is easiest. If you're topping up frequently, you have a leak — get it investigated before it overheats the engine.
Signs of trouble
- ⚠Coolant warning light or temperature gauge climbing into the red
- ⚠Sweet syrupy smell from the engine bay
- ⚠Coloured puddles under the car when parked
- ⚠Cabin heater blowing cold
- ⚠White steam from under the bonnet
- ⚠Repeated need to top up the expansion tank
£0 to check; £8–£20 to top up
Always get a written quote. Prices vary by car, region, and parts brand.