Coolant: level and checks

Coolant circulates through the engine and radiator to remove heat. Low level or a leak can cause overheating and engine damage. Here is how to check the level and when to act.

Where to check the level

The expansion tank (translucent reservoir) is usually next to the radiator under the bonnet. Find the min and max marks: the level should be between them, engine cold. When hot, the level rises; do not open the cap when hot (risk of burns and spray).

When to top up

If the level is below minimum, top up with coolant that meets the manufacturer’s specification (colour and type: often pink/green/blue depending on type). Do not mix different colours or types without checking compatibility. Water only for emergency use (risk of freezing and corrosion).

Level keeps dropping

A repeated drop in level indicates a leak: hose, radiator, head gasket, water pump. Have the system checked by a professional. Do not ignore: a leak can cause overheating and engine failure.

When to replace coolant

Coolant degrades over time. Manufacturers recommend replacement every 2–5 years or 30,000–100,000 km depending on model. A full drain and refill keeps the system clean and protects against freeze and corrosion.

Order of magnitude for costs

Topping up: a few euros. Full drain and refill: €50–120. Leak repair: variable (hose €50–150, radiator €200–500, head gasket much more). My Auto Check-up helps you track levels and maintenance to anticipate costs.