Virginiafiretruck,
You probably already know these facts. The thermostat is directional. If has to go in with the spring or pellet facing the 'hot side' (I think).
Coolant flow is from radiator through bottom hose and engine, out through top hose into tank.
If the system is blocked...thermostat not open, coolant cannot circulate through upper hose into the tank.
If the thermostat is stuck, in backwards, or sitting in a air pocket, it can't open. I can see no reason a brand new thermostat wouldn't function properly. Lots of folks toss them in a pan of hot water on the stove just to verify that they are opening..ye of little faith!
Check things out and give it another try...'good on you' for watching the temp gauge!!
Stuart
