Coolant-temperature warning
An overheating warning while riding requires a safe stop and engine shutdown; never open a hot pressurised coolant cap.
Last reviewed: 23 July 2026 · Exact behaviour varies by make, model and year
Normal behaviour
The symbol may illuminate briefly during the ignition self-test. Some dashboards also show temperature bars or a numerical reading before the warning threshold is reached.
Possible fault
If the warning remains on or appears while riding, the engine or cooling system is too hot. Continuing can damage the head gasket, cylinder head, pistons or other components.
What to do
Reduce load, stop safely and switch off the engine. Allow the motorcycle to cool. Never remove a radiator or pressurised expansion-tank cap while hot. Once fully cool, use the handbook to identify the correct reservoir and checking method. Arrange recovery if coolant is leaking, the level is empty, the warning returns or the cause is uncertain.
Possible causes
- •Low coolant or a leak
- •Radiator fan, fuse, relay or temperature-sensor fault
- •Thermostat or water-pump problem
- •Restricted radiator airflow or damaged fins
- •Cooling-system airlock or incorrect filling
- •Extreme operating conditions combined with another issue
When not to ride
Do not continue if the warning stays on, coolant is escaping, steam is visible or the engine runs abnormally. Do not leave an overheating engine idling as generic advice; follow the model handbook.
Sources
- The Highway Code, warning displays and vehicle maintenancehttps://www.gov.uk/guidance/the-highway-code/annex-6-vehicle-maintenance-safety-and-security
- Honda motorcycle owner's manualshttps://www.honda.co.uk/motorcycles/my-bike/honda-motorcycles-owners-manuals/
- Yamaha motorcycle owner's manualshttps://www.yamaha-motor.eu/gb/en/service-support/owner-manuals/