Impurities and/or solids in any liquid can assist cavitation as well as surface irregularities, but like I said, the 4.0 physically can't spin the impeller fast enough to create cavitation to begin with. It does happen often in vehicles with engines that can spin well past 6k rpm, older rx7's for example. You could create cavitation with a smaller pulley and a restricted inlet on the 4.0 though, that along with a lot of free radicals floating around, like you say, would be catastrophic.

 

Kalali - heater control flap functions perfectly. Problem is no coolant flowing in / out of heater core.

Firestorm500 - Coolant only glows when I shine one of the kids black light toys over it. Think someone put UV dye in the system at some point. Also the driveway is rust stained everywhere the coolant touched.

PocketsEmoty - Still no heat

Changing out everything now would not be my first choice. Jeep does not over heat at idle in the driveway but driving it in single digits with out heat is not going to happen. I'll park it and keep driving my 2500HD until it is a little warmer.

The more I think on these conditions, no heat, cold lines to heater core, regular surging of coolant once hot and radiator cap is left off while engine is running, and previous summer driving feeling the engine was running hotter than it should, I really will be shocked if there is more than one vane left on the water pump once I take it off.

Thanks again for the suggestions. I'll update with a picture once I take the pump off the engine.

 

So yeah... I was able to get the old pump off today. Barely one vane of the water pump was still left intact. Bearing fine. Seal fine. Just no vanes left to actually pump coolant.
So now that the temperature is dropping I think I will wait until next weekend to get the new pump installed.
Thanks again for the info on this as I would have not thought about the pump being bad with out it leaking.

 

New pump installed, block flushed, heater core flushed, newly installed radiator flushed, all several times in opposing directions until water ran clear. Hooked up air compressor to blow out as much water as possible after that.
Did some other cleaning and scrapping while things were apart as well.
For changing the pulley it worked well to have a ratcheting wrench rest against the socket wretch to keep everything from spinning while tightening or loosening the bolts.
Engine warmed up normally. Test drive showed no issues and heat flow inside cabin was great! Temperature gauge moved very little between the 210 mark and the mark just before 210.

 

Gotta love a good heater in the winter!