[Cobra20646]

I really don't see much of a problem. What kind of cooling fan are you using. Does it run all the time or come on at some preset temp?
The only problem I see from your symptoms MIGHT be a sticky thermostat...... opens, but later than 180 degrees, and that's stretching the point, or a fan that has the preset temp set too high.
You said "Then, if I make a short stop (10 minutes or less), when I start the car, temp immediately shoots back to 220+, once again, until I get underway. " this is indicative of electric gauges and is normal. When you shut down the engine, the water does not move through the system (well not much anyway) and the temperature of the water in the block rises. The temp gauge, being electric, when turned on by the ignition switch will then shoot up, and then return to normal after the water has a chance to start circulating again. A manual gauge will do the same thing, but you can watch it while the engine and the ignition is off.
With my own car, when the engine is running and I'm sitting still, the temp will rise over 200 to about 210 and stay there... even with the electric fan... and then return to normal after getting underway again, with better air flow and higher RPM at the water pump.
The only reason to drain and refill the radiator is if your unhappy with the "type" or condition of the coolant. You won't gain anything if your just tring to expel air.
- Jim -