The "orifice tube" is located in the "condenser to the evaporator' line. The orifice tube will change the high pressure liquid refrigerant into a low pressure liquid refrigerant. Once you seperate this line at the stationary fitting and flare nut, you can pull the orifice tube out with a pair of needle nose pliers. Try not to break the old one while removing it or you will need to get an extractor tool from a parts store. Change out the old O-rings with new ones and coat the new ones in refrigerant oil prior to installing. Installation is the reverse of removal. When done with repair, do not forget to have the system evacuated with a vacuum pump, making sure it holds it's vacuum reading for a period of time (meaning no leaks in system), then recharged fully with refrigerant which should be R-134A. Note, I've looked thru my Haynes Manual and it doesn't mention anything about Explorers with rear cooling having a rear expansion valve or orifice tube. They do have a rear heater core for heat, but nothing mentioned on a rear evaporator. So according to the manual, the orifice tube you are looking for would be under the front hood of the vehicle in the line between the condenser(located next to the radiator or vehicle front) and the fire wall. The evaporator would be located behind the inside dash of the vehicle. Hope this helps!