Abstract: A heat exchanger includes an adapter header plate having a row of coolant openings, an adapter tank having a lip aligned with a heat exchanger core header and tubular protrusions corresponding to the coolant openings of the adapter header plate. Elastomeric grommets are inserted into the coolant openings of the adapter header plate for sealing the coolant openings to the tubular protrusions of the adapter tank. The heat exchanger includes an elongated filler frame member having an opening extending therethrough and opposing lips extending around each end of the opening. At least one tab of adjacent heat exchanger cores are secured to the filler frame member lips to connect at least two of the heat exchanger cores. A pair of opposing side members and a core support member centered between two heat exchanger cores are adapted to direct air flow to the fins and tubes of the heat exchanger cores.