Where is the radiator cap located in a 2002 Jeep liberty sport?

The radiator cap is actually on the plastic overflow bottle located on the passenger side of the firewall. It is pressurized while it is hot, so, use extreme caution there. Your best bet is simply to let it cool before removing the cap.

*On a side note* If you are adding a radiator or cooling system sealant, Do not add it to the overflow jug, instead, remove the upper radiator hose (drain out a bit to ensure there is room in the system for what you are adding) and add your sealant there, re-attach, and then start the engine. I hope this has helped, good luck!!