Abstract: A heat exchanger apparatus includes a first and second coolant tanks spaced apart from each other, a plurality of heat exchanging tubes extending between the tanks for enabling coolant to flow from the first coolant tank to the second coolant tank and to be cooled in said tubes, and a coolant supply/return tube for enabling coolant to flow from the second coolant tank to the first coolant tank. The supply/return tube has a substantially circular cross-section. The supply/return tube has opposite end portions inserted into complementary openings in the inlet coolant reservoir and the first tank. In order to provide the proper, predetermined orientation of the supply/return tube in the heat exchanger apparatus, the supply/return tube has opposite locating members each adjacent to the end portions of the supply/return tube, so that a small, predetermined length of the end portions of the supply/return tube protrudes inside the supply/return tube.