I have 2006 Uplander. I got it in August. The temp. gage was in the middle and steady. Then once goes up by one quarter, then the coolant level was dropped by an inch. During the winter it rundownby a quarter and back to the middle continuously.Under -15C heat was great, aboveweak. At -4C the coolant temp. run from 80-89C. Now it goes up by a quarter and down by a quarter from themiddle. When I take a right turn, there is no heating, the temp gage goes up, on the left there is heating, temp gage goes down.
There is almost no heating in the morning despite of the gage showing in the middle, normal engine temp.
Is there anyone has the specification for the thermostat? Is there an air bubble in the system? Any thoughts?

 

do you still have the heat problems