You changed the water pump? There is a plastic tube that is well known to be difficult to seat correctly. It's on the back of the pump and you can't see it.
I would go back in remove the water pump to check. The V-8 and V-6 use the same block so the water pumps are also the same. Look up some threads on water pumps to see pictures of what your fighting.
Now this also brings up the question did you replace all the plastic tubes on the engine? They all decay and fail. You may have a failed plastic piece too?

Really recommend you look up "Big Will". He has posted great repair threads with pictures. Including the water pump/cooling system.
One last thing? DO NOT allow the engine to overheat. Many threads on this and the real problem is it's hard to tell because the temperature gauge is just an indicator and NOT a real temperature gauge!

Please come back with answers because many 1 post posters never reply and we are just left hanging?
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Right but that's the exact problem. You changed it but can't tell if it is seated correctly in the back of the pump.

If you need to remove the SC the tough part is the alignment pins. They stick the SC to the engine and can be a bitch to break free.
Again we have SC removal threads with pictures. Big Will has some of the best.
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