The radiator is a new Champion, and I paid just over $200 for it delivered, from Champion.

I will drop the pan and look for antifreeze. I will also vacuum test the trans cooler part of the radiator. That is going to be a pita on his truck.

I was talking with my son (whom I got the motor/trans from) and there is a possibility that the torque converter may have gotten some rain water in it. It was out of the trans, sitting on the floor, with just a paper towel covering the opening. He had the roof replaced on the garage. In the process of replacing the garage roof, we had some pretty heavy rain for a couple of days. He thinks maybe the converter was exposed to rain when the garage roof was open. We are not sure of the timing of weather or not the trans was in the garage at the time the roof was replaced.

When I got the trans, the fluid in the converter looked normal, but if there was water in it, the oil would have floated to the top. Wouldn't have taken much water in the converter to give me this problem, and it would have taken a while for it to mix with the other fluid to give me what I now have.

If I find no evidence of antifreeze in the pan, and I drain the cooler lines and test the rad, and its OK (a guy can dream, right?) I'll add an outside cooler, replace the pan, add fluid, and run it a few minutes, the repeat, will that be enough to flush the system, or should I just take the truck someplace and have it flushed?