What main advantage does the use of a closed, sealed cooling circuit in the engine provide?

Question

DentroTest · Accepted Answer

In current engines, the cooling circuit is closed and sealed, working under a slight controlled overpressure regulated by valves in the cap of the expansion tank. This design raises the boiling point of the coolant above 100 ºC and avoids continuous contact with the outside air, which drastically reduces coolant losses through evaporation. By contrast, antifreeze is still necessary, because the freezing point depends on the antifreeze concentration and not on whether the circuit is closed. Nor can the fan be dispensed with, because it remains an essential element for forcing air through the radiator at low speeds or at idle.

What main advantage does the use of a closed, sealed cooling circuit in the engine provide?

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