TexasCHLforum.com

Why was the thermostat not replaced along with the radiator, or even with the subsequent water pump? Any time a car has overheated, the thermostat has been compromised. Thermostats are cheap; it costs more to test one than it does to just go ahead and replace it. . Replacing it is cheap insurance, which is why it is the best practice to replace it along with any cooling system repairs.

Never run a modern car without a thermostat. It is too much to go into here, but you can end up causing engine damage over the long haul.