coolant pump bypass? on 2003 Lincoln Town Car

I am told that when the coolant thermostat is closed the coolant bypasses so it flows back to the engine.
Question: Is there a valve to control the bypass? If not what controls the bypass vs the flow through the radiator?

Asked by for the 2003 Lincoln Town Car
The thermostat restricts coolant flow to the radiator when the engine is cold, as it warms up the thermostat allows the coolant to flow through the radiator. I hope that helps!