How does a thermostat that is mounted at the inlet to the engine and outlet side of the radiator work because when it opens it is then exposed to the colder water from the radiator?

Answer 1

The thermostat opens to allow the hooter fluid in the engine to escape to the radiator and be colled by the air passing thru the fins of the rad. It is then pumped via the water pump from the bottom of the rad back into the engine. I think you had your routing wrong.

WHEN YHE ENGINE HEATS UP TO 180 OR 190 DEGREES DEPENDING ON THERMOSTAT.THE THERMOSTAT OPENS AND STARTS TO CIRCULATE IN RETURN COOLINS ANTI FREEZE.....HOPES THIS HELPS

The inlet thermostat doesn't operate that much differently than the outlet thermostat does. Both allow the engine's coolant pump to pull in cooler coolant from the radiator when the thermostat first opens. The outlet thermostat will get less of the radiator's cooler coolant because it will have mixed to a greater degree with the hot coolant already in the engine. The inlet thermostat will be exposed to a relatively higher amount of radiator's cooler coolant and likely not open as much initially and not go through as many opening and closing cycles as all of the coolant in the system warms up.

The bigger operational difference is that the inlet thermostat will have to have some means to sample the warmer coolant circulating in the engine via a dedicated bypass or other hose. The outlet thermostat will not need this because it is usually integral to the engine block coolant passages and readily gets warmed coolant routed to it.