How is the flow of coolant to the radiator interrupted while the engine is still cold?

Question

DentroTest · Accepted Answer

The thermostat is a heat-sensitive valve located in the cooling circuit whose main purpose is to regulate the operating temperature of the engine. When the engine starts cold, the thermostat stays closed to prevent the coolant from passing through the radiator, recirculating it only through the engine block so that the engine quickly reaches its optimum operating temperature (generally between 85 °C and 95 °C). The coolant pump is not disconnected (it keeps driving the fluid continuously) and the relief valves only control overpressure in the circuit, not the flow to the radiator.

How is the flow of coolant to the radiator interrupted while the engine is still cold?

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