Engine cooling by nucleate boiling requires a profound knowledge of cooling systems components: heat exchangers, water pumps, eventually liquid-vapor separators, on the part of equipment manufacturers. Experimental and theoretical studies of the principal heat exchanger, I.E., the vapor-condensor, were effected. The experimental phase required the development, after careful study, of a test set-ups specifically designed for vapor-condensors. Tests are conducted under controlled intake pressures and temperatures, and sub-cooled outlet conditions. Under varying air-flows, outlet-liquid measurements yield instructive information relative to exchanger thermic performance. The influence on performance of tube shape, direction of liquid circulation (horizontal or vertical) and number of passes was also studied. Concurrently, thermic visualization by infra-red camera permits qualitative evaluation of vapor distribution within the condenser. Thermic models based on exchange condensation theory permits comparisons between theoretical models and experimental results. We enunciate expected gains in performance and space-requirements due to the use of boiling liquid cooling systems.