when you go t get the water pump buy some coolant flush also. dump it in the radiator and let the jeep run for awile,the instuctions should say how long. also find out if your jeep uses the long life coolant and get that pre mixed with water(3 gallons is what it holds i think).the long life coolant is used in alot of the new cars it has different chemicles in it that is more effeciant.if you ran the regular ethenol (green )antifreeze with the long life it may have cause the problem.it leaves all sorts of nastiness behind.
after you run the coolant system flush drain the system completly and flush it out with a water hose.i would also remove the thermostat before flushing,you dont want any garbage messing it up. then after all that is done
reinstall the thermostatand install the new waterpump then fill it up.let it run for awile then turn it off and let it set so any trapped air can escape.repeat until you cant get any more coolant in the radiator. i hope you get it figured out soon heat stinks.