Abstract: A method for joining an inlet/outlet pipe to a heat exchanger core in which a standard coupler of stepped cylindrical shape is first brazed integrally to the core. A unique pipe is then attached inside the outer end of the coupler purely mechanically, with a compression ring that is forced axially over the outside of the coupler to compress the inner surface of the coupler against the outer surface of the pipe. The axial force is applied between the ring and an integral bead on the coupler, so as to protect the coupler braze joint from damage.