Engine Coolant Level Low

Possible causes

• CommonCoolant genuinely low, from a leak or from being burnt
• CommonFailed coolant level sensor or float
• CommonCorroded connector at the expansion tank
• PossibleWiring damage
• PossibleLoss of reference voltage or earth
• PossibleSensor coated with deposits from old or wrong-specification coolant

What you might notice

• Coolant level warning
• Engine running hot
• Heater blowing cool
• Sweet smell of coolant
• Visible coolant loss or a puddle under the car
• Check engine light on

What to check, in order

1. Check the level when the engine is cold and top it up with the correct coolant specification. Never open a hot cooling system.
2. Find where it went. Topping up without finding the leak means doing it again, and next time possibly not in time.
3. Look underneath, around the hoses and water pump, and in the passenger footwell - a heater matrix leak shows as a damp carpet and a persistently misted screen rather than a puddle.
4. Watch the temperature gauge closely until this is resolved, and stop if it climbs.
5. If coolant disappears with no visible leak, have a head gasket test done. That is the expensive possibility and it is worth confirming or ruling out early.
6. Use the coolant specification the manufacturer names. Mixing types can cause them to gel and block the radiator.