Best way to figure it out: pressure test the system (test kits available at pretty much every auto parts store). Test will help you figure out where the leak is coming from. Fix the leak and if applicable, replace the component(s) it's leaking from since you're opening it up from there anyway. Finally, flush the cooling system and refill.
IMO that's the best way to go about it as opposed to just randomly throwing parts at the jeep and hoping for the best.