Process and apparatus for cooling internal combustion engines

Apparatus for cooling an internal combustion engine comprising a coolant jacket around at least part of each combustion chamber and exhaust runner of the engine and containing a boilable liquid coolant having a saturation temperature above 132.degree. C. at atmospheric pressure, a liquid cooling circuit including a heat exchanger and mechanical pump means for circulating the coolant from the coolant jacket through the heat exchanger and back to the coolant jacket to provide heat rejection in the heat exchanger such that no vapor is formed in the liquid cooling circuit as a result of the pressure drop induced by the pump and such that the temperature of the coolant within portions of the head portion of the coolant jacket that are in elevation above locations adjacent to combustion chamber domes and exhaust runners are maintained below the saturation temperature of the coolant for the system pressure, at least one outlet from the highest region in the coolant jacket adapted to remove and release continuously by substantially unrestricted convection from the coolant jacket substantially all gases, including vapor formed by localized boiling of the liquid coolant in areas adjacent to combustion chamber domes and exhaust runners, other than gases that condense in the coolant within the jacket, whereby the major part of the coolant jacket in areas around combustion chamber domes and exhaust runners is kept filled with coolant in the liquid phase at all times, condenser means including a condenser chamber for receiving the gases removed and released from the coolant jacket through the outlet and condensing condensable constituents thereof, and return means for returning the condensate from the condenser means to the coolant jacket.