Purpose of the thermostat (Audi A4 B5)

Simply put, the thermostat is designed to determine whether the liquid in the radiator needs to be cooled or not, i.e. it "decides" whether the coolant should circulate in the "small" or "large" circle, which was already discussed at the beginning of the chapter.

The thermostat regulates the flow of coolant depending on its temperature. As long as the coolant temperature rises, the thermostat increases the flow of cold liquid from the radiator. Conversely, if the operating temperature drops, the thermostat spring again presses the valve plate to the "closed" position (German: "Zu") and thus blocks the flow of cooled coolant until the operating temperature rises again.

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