OVERHEATING

If the thermostat opens at 180* true, and the coolant heat keeps climbing, then there isn't enuff cooling capacity, sure it'll creep up to 200, but it shouldn't.
If it creeps, something is deficient, and when you "work" the engine creating more heat, the temp will continue to rise till overheat.
Once the thermostat opens at whatever temp, that is the temp it should stay , uphill, in traffic, at a stoplite . .