99 suburban rear coolant lines block
 

99 suburban K1500 5.7L LT
I recently took the rear AC and heater unit out of the back, and hacked through the lines without anticipating the coolant lines being there.
I put in loop under the passenger side door to loop the coolant back to the engine, but I'm wondering if anyone knows the location of the start of these lines, and how to block them there and how to block them off? I also need to block off the rear AC lines, but that's less important. (My loop has a tiny leak, which is the whole point of this exercise).

There should be a 'T' connector under your hood near the front heater. And maybe even a valve assembly.