Coolant Warning Light Meaning and What to Do
The coolant warning light (a red thermometer or wave symbol) means your engine coolant temperature is dangerously high, or coolant level is critically low. Pull over safely and turn the engine off — continuing to drive risks warping the cylinder head or cracking the engine block. Do not open the radiator cap on a hot engine.
Common causes
Get a detailed AI diagnosis
Add your vehicle details and any extra context for a personalised analysis — likely repairs, cost estimates, and questions to ask your garage.
Common questions about: Coolant Warning Light Meaning and What to Do
What does the coolant warning light mean?
The coolant warning light (usually a red thermometer or wave symbol) indicates your engine coolant temperature is too high, or the coolant level is too low. Both are serious and require immediate attention.
What should I do if the coolant light comes on while driving?
Pull over safely as soon as possible, turn the engine off, and let it cool for at least 30 minutes before checking the coolant reservoir. Never open the radiator cap on a hot engine. Call a breakdown service if in doubt.
How much does a coolant system repair cost?
Costs vary widely. Topping up coolant costs almost nothing. A thermostat replacement costs £100–£250. A water pump replacement is £200–£500. A blown head gasket — the most serious cause — can cost £800–£1,500+ and is often uneconomical on older vehicles.
Can low coolant cause permanent engine damage?
Yes. Continued driving with the engine overheating can warp the cylinder head or crack the engine block. Always stop immediately if the temperature gauge reaches the red zone.
Got a quote for this repair?
Check every line in 60 seconds — labour hours, parts prices, and regional rates.
Check My Quote Free