Abstract: The invention is an improved cooling system for an internal combustion engine wherein an expansion and degasification tank is placed in the cooling system allowing the liquid containing gases to enter the degasification portion of the tank tangentially thereby creating a swirling vortex flow of the coolant containing gases. The coolant is permitted to leave the degasification portion through a peripheral annular gap in the lower part of the tank created by a conical deflector which collects the gases in the coolant and is arranged so as to permit the gases to pass to the expansion of the tank. A check valve mounted in the outlet of the expansion tank prevents any backflow of liquid. Further, the gases are allowed to escape into the atmosphere through a pressure release valve mounted to the top portion of the expansion chamber.