Thank you for your input . I do think maybe the eye got jostled off in transport..the furnace was laying on its back and the eye probably came loose. I will replace it and see what happens. The furnace will only run about 30 to 45 seconds and shuts off. Thank you again!
thanks for the kind words and all of your help. i guess you saw the finished product that mcsteamer22 posted. that was our project this past wednesday and thursday. SO MUCH little stuff had to be done. replacing cage elements. freeing up seized hand valves at the radiators and installing new seats in every one. i thought the incidental stuff was never going to end. and like you said about the 3" cap on the loop. brave men AND big wrenches!!!! thanks again for telling us everything we needed to know about the differential loop.