Are you sure. My heater leaked at the core after the dealer installed the new hoses and routing design, but after much searching I found out the dealer clamped it to close to the heater and the pipe changes size as it goes into the heater box. You need to leave like 11/2" space between the heater box and where the clamp goes. It took several tries but I got it sealed up no leaks and I was sure it was the core too.
