Maybe it helps or not, but last week we had an air lock in the coolant system (I changed the hoses and had the HX cleaned). After a few minutes on the engine, the temperature gauge read over 200, but the engine was not particularly hot. Was that really the engine? The gauge? Finally we found that there was no coolant in the thermostat housing so the probe was taking the temperature of the air (which heats up faster than the liquid I imagine). Conclusion: I bought a laser thermometer to get a second opinion if my instruments tell me that the engine is too hot.