How does a radiator of a vehicle cool the vehicle engine

Fluid is pumped from the radiator through passageways in thee engine block. The fluid absorbs heat from the engine. The fluid is then pumped back into the radiator. The radiator is simply an efficient heat exchanger. Air is pulled through the radiator and absorbs heat from the fluid. This cools the fluid.

The thermostat regulates the amount of fluid pumped through the engine. When the engine is cold, the thermostat allows almost no fluid to be pumped. As the engine warms, the thermostat opens.

The water pump pumps the fluid around the circle.