Abstract: Cooling circuit for internal combustion engines, with an excess-pressure valve which, when the cooling circuit is under full thermal load, limits the pressure in the feed to a value at which the pressure on the suction side of the coolant pump is always above the boiling pressure of the cooling medium, even at full delivery level of the coolant pump. The efficiency of the cooling function is improved as also the structural expenditure in connection with the cooling circuit is reduced thereby and also by the central arrangement, in the filling stub, respectively, the cap thereof, of additional excess-pressure and vacuum valves, of a throttle for a venting flow, of a level float switch for the filling level indication in the cooling circuit and of a blocking device against the opening of the cap which is under pressure.