99 Range 4.0 heating problems

[outback]

My temp gauge jumps up as normal but goes almost to the red overheat area then bottoms out. When the gauge bottoms out the heat disappears with it. Coolant system including heater core have been flushed, new radiator cap and new thermostat put in. Not loosing coolant not blowing smoke and oil appreas to be normal, engine seems solid with no missing or power loss. I have read other threads that speak of similar symptoms but they were not loosing heat inside the vehicle, when this happens I start blowing cold air then the gauge jumps back up and I have heat and the cycle just keeps repeating. Any help greatly appreciated.

 

[martin]

Sounds like a sticky thermostat.