Gets hot enough to blow steam through the pressure cap into the reservoir. There may be a problem here, but I am really doubting it. The purpose of the reservoir is to allow coolant to go in when cold and out when reaches operating tempeture and compensates for the surge of the thermostay opening. I remember my *-10 hitting 225 by the gauge briefly at times , full of quarry stone in the summer, and not blowing the relief valve in the pressure cap. If the car has a new thermostat, runs ok, and holds coolant.... I would drive on. Did the full time fan switch help?
Have you tried something as simple as replacing the radiator cap? From what I read, it sounds like the same thing that happened to me in my Bonnie just last spring. I tested the thermostat, It was ok, The water pump was new, and so was the radiator. So, replacing the cap was the last resort. So, thats what I did. It worked!