My truck has been over heating, and I cant figure out whats going on...the only thing that gets really hot is the upper radiator hose, and the radiator....I just noticed there was a plug unhooked from the water pump, what does that do? Or maybe it could be the thermostat? It just overheats, and when I park it, it wont start half the time, usually I can let it cool off and go, but sometimes it just dies and I have to let it cool off and jump it off.
Most likely the thermostat. If there is no leak that's most likely. That plug could go to the fan sensor, but I think F-150 fans were belt driven. More likely it goes to the temp guage. If you have an electric fan, check to see if it goes on.
Get yourself a Haynes or Chilton repair manual at Autozone, Pep boys, etc. Make sure you clean the old gasket material completely off the block before you mount the new pump. If not, you'll leak and have to do it all over again.
Based on what you said about it overheating and the upper radiator hose and radiator being the only hot parts, it is definantly a thermostat issue.
I doubt its your water pump. That plug may have been just the temperature sensor. Definitely sounds like a bad thermostat. Replace it. They aren't expensive at all. Letting your truck over heat does serious irreversible damage to the engine. You may have significantly shortened the life of your engine already. Just replace the thermostat when the truck is COLD, never when its hot. If it still overheats with the replacement thermostat, your radiator may be clogged.
