<p>The circuit (1) has a cooling radiator (7) comprising a discharging outlet and an inlet connected to an outlet of a water outlet case (3). A thermostatic valve (5) selectively blocks the flow of cooling liquid between the water outlet case and the radiator. Another thermostatic valve (4) comprises a wax cartridge and selectively blocks the flow of the cooling liquid between another outlet of the water outlet case and an inlet of a degassing case (18). The latter valve is closed when the temperature of the cooling liquid exceeds a threshold value ranging between -5 and 200 degree Centigrade.</p>
