I have had a issue with the blue coolant light on the dashboard. First on a cold night it can take up to 6/7 miles to go out, second I have had the coolant light come on after going downhill then after a few miles go out, third the heater never feels hot compared to my van. Today going down hill the light came on, then after about a mile went out. By the time got home (about 2 miles) the heater was blowing very warm air out, lifted the bonnet and the top hose was hot to touch and the bottom hose was warm as well. Been to my local garage he says it is the sensor, I am not convinced. Has anyone out there got any ideas.