Fan kicks in extremely late!

[Red Ceri]

I can't remember where in relation to the thermostat hot side the Temperature sensor is but it sounds like that either the Thermostat is not opening or there is a massive air lock in the system preventing hot coolant getting to the temperature sensor and thus the reason the fan is not kicking in is it is relying on surrounding parts getting hot and not the flow of hot coolant over it.


Worst case scenario is water pump failure, thus not pumping hot coolant around the system and  past the temperature sensor.