A cooling system for vehicles having a modular roof-mounted, low profile compartment and at least one radiator core mounted for horizontal extension but at a slight angle to the roof as well as being spaced above the roof with fans arranged alongside each radiator core for drawing air into the compartment and across the cores, then upwardly and away from the cores and compartment; and coolant lines extend between the cores and different components to be cooled in the vehicle. The radiator cores may be arranged to extend lengthwise along opposite sides of the roof or may extend transversely, and a battery system for a hybrid engine may also be mounted alongside the radiator compartment and in the same manner as described with respect to the radiator cores, the battery compartment being representative of other utility components that may be similarly mounted in low profile compartments.