QUOTE=svx_commuter: "From what you say this could be a head gasket leak"
My thoughts exactly, this isnt a stupid question at all, rather a most frustrating pronlem that i myself have lived through with an earlier model liberty.
I flushed the radiator, had it flushed profesionally, repalaced all coolant hoses, went through 3 thermostats, 1 water pump, 20L of coolent, and a **** load of stress!
Do what these fellas sugest first, but worst case senario is a head gasket gone!
On liberties if the gasket blows on the exaust side it can be very hard to tell, mine didnt even show up on pressure tests! Are you loosing coolant??
the problem got worse and worse untill more visible signs appeared such as oil in the coolant (six - eight months after first overheating incident)
I got around by drilling 3 holes in the thermostat so the car always ran cool! (no heater sucked in the winter)
If you want more answers and how tos try this forum and search around a bit, loads of info here
http://www.rslibertyclub.org
cheers,
Jake