The temp gauge "bouncing around" is typically a pretty good sign there is air in the system. Needs to be burped.
I know and read about a lot of Jeep owners replacing water pumps, radiators, fan units, etc., but in my experience those things rarely go bad and I hate to see people spending their hard-earned dollars replacing stuff that probably isn't necessary.
Why and what was the reasoning behind replacing the radiator? Other than being a holding container for coolant and cycling it through the loop, it has very little to do with actually keeping the engine cool... unless the radiator is actually leaking.
And I guarantee the temp "bouncing around" was because the dealership simply put a new radiator on it and filled it with coolant without burping it. As was stated before, get the front tires up off the ground a good 6" on a parking curb, jack stands, ramps, whatever. With the engine cold, remove the rad cap and let the air bubbles burp out. If the coolant is not in sight when you take the rad cap off, add coolant slowly a cup or so at a time and let it force the air up and out.
