Abstract: Difficulty in heat exchanger module replacement and the cost of plural manifolds in a modular heat exchanger useful in heavy duty vehicles or the like is avoided in a construction that includes an elongated manifold (20) having spaced interior inlet and outlet channels (84, 86) along with a plurality of spaced inlet and outlet ports (68, 70) in fluid communication with respective ones of the inlet and outlet channels (84, 86). An elongated frame member (14) is spaced from and parallel to the manifold (22) and has a plurality of spaced retaining formations (42). A plurality of heat exchanger modules (12) are mounted between the frame member (14) and the manifold (20) in side by side relation and each module has spaced tanks (34, 36; 50, 52) with a plurality of finned tubes (30, 32) extending between and in fluid communication therewith.