Okay, so here's the latest.
My mechanic went over the top and bottom of my engine looking for leaks and did that test for exhaust gases in the coolant with that blue chemical/liquid that's supposed to indicate if you have a leaking head gasket. That came back negative. In other words the blue liquid stayed blue.
So what we're going to do is flush the engine and replace the radiator and the thermostat.
Now I got that used/refurbished radiator about a year-and-a-half and 15,000 miles ago. I believe the guys at the shop where I got it from to be honest and they seemed to do good work. I've used them before.
However, in the end, you really don't have a good history, or history of any sort, on a used radiator so you have no idea how well it was maintained internally along the way or even how many times it may have been recycled for that matter. So we're just going to skip the guesswork there and go for a new one.
And then, after all is said and done there. we will see.