When the engine is cold, the thermostat is closed, restricting coolant flow. This allows the coolant to heat up quickly, bringing the engine to its optimal operating temperature. Once the engine reaches its optimal temperature (usually around 195-220°F or 90-100°C), the thermostat opens. This allows coolant to circulate throughout the entire cooling system, including the radiator. The radiator then dissipates the heat into the surrounding air, resulting in a stable and lower engine temperature. The temperature stabilizes around the set point of the thermostat.
