Incidentally, the inlet and outlet pipes, filler neck, or other members of the first and second heat exchangers are omitted in the drawings.Tanks 25, 27 of the first heat exchanger 21 and the tanks 31, 33 of the second heat exchanger 23 are integrally molded from aluminum (e.g., A3003) by extrusion.The tanks 25, 27 of the first heat exchanger 21 have rectangular cross sections, and the tanks 31, 3