I would start with a new water pump and a good flushing of the cooling system. Swap to a 180 T-Stat as well. Attach a real temp guage as well and see what the real temp actually is.

Are you loosing water? Any in the oil?

Added: Check the lower rad hose for collapsing as well.

If it has got as hot to melt that stuff, I would also be worried about the engine. It does not take a lot to distort bores and/or to start swapping metal.