Thanks everyone. It's fixed now - I'm not sure exactly what the problem was, but it wasn't the radiator. It needed to be cleaned out because it had a lot of goo in it. But after I cleaned it out, the problem still existed. Then I ran a roto rooter toilet snake through the water jacket of the engine block AND took out the thermostat. The thermostat was new. Those last two things (running the toilet snake and removing the thermostat) allows the engine to run without overheating.
It certainly could have been an air pocket behind the thermostat. But, the radiator, water pump and engine block needed to be cleaned out to get that gunk out. The sealant did its job of sealing the tiny water leak from the head gasket. And although I had to do a lot of work, it was still less work and more comfortable work than pulling the head again.
Harrell
