What an incredible write up! Thanks so much for taking the time. Now I see why the cheapest place I've found to replace the heater core wants $800 to do it.
I have always hated doing heater cores, but I think this quite possibly may be the worst I'll ever attempt. I think I had less aggrivation replacing the motor in my 98 Cobra than I'm going to have replacing this heater core
I had flushed the system with water and tried some of that stop a leak crap, but I couldn't tell if it worked. The leak seems to be rather small, the level in the radiator overflow doesn't go down and there is no fluid on the carpet. I see now how I was able to still smell antifreeze with the A.C. on with that huge enclosure for the 2 cores.
One question I do have, I was told this 99 Navigator had 2 heater cores, where is the second?