[BILL WILLIAMSON]

The ONLY time you DON'T need a thermostat, is if you have a crummy Old Radiator that quickly warms up, on its' OWN!
Remember, the engine is a water HEATER, the radiator is a water COOLER & a thermostat is needed, to co-ordinate the workings of the two systems!
Hope that is SIMPLE enough to be understood!
Early thermostats were prone to failures, that why Henry didn't use them, until some design upgrades made them somewhat MORE RELIABLE. He should have left a NOTE about it, on his Office Wall!
Bill Simple