Abstract: A deaeration system for a cross-flow radiator requiring continuous deaeration utilized with an internal combustion engine, wherein the radiator includes a vertical inlet tank and a vertical outlet tank connected by a tube and fin core. A generally vertical baffle divides the outlet tank into two compartments, one of which functions as a receiver tank for the core while the other compartment functions as a reservoir tank having a filler neck for a cap and pressure relief valve communicating therewith, and the radiator fluid outlet communicates with the reservoir tank adjacent the bottom thereof.