I just went through this exercise of fixing a freon leak on my 97 4.0 Ranger. Last year I replaced Compressor and Receiver Drier. This year freon is gone, no apparent leaks. Installed a can of freon with dye to locate leak-nothing seen.
Summers too hot in Florida and needed a/c to work so I took it to an a/c shop. They also installed two cans of freon with dye and called me to show where the leak was. It was in the a/c hose running from the receiver drier, across the back of the firewall and then connected to the compressor outlet. The metal piping within the hose is insulated with a very thick foam insulation. They had to use an electronic sniffer to indicate where the leak was in the hose. The metal pipe hidden beneath the heavy insulation had rusted through. Estimated price to fix was $600. I paid the shop $80 for the analyzing to locate the leak and the two cans of freon/dye used.
Note that this particular hose with the heavy insulation is only used on the 95-97 4.0 engine powered Rangers.
I then called my son who is an amateur mechanic for an assist. I ordered the special hose from O'Reilly auto parts for $125 and a couple of cans of freon. I was able to use my fairly new receiver drier. The installation took my son and I about three hours to remove and install the hose, evacuate the system and recharge with two cans of freon.
The original hose is attached to the firewall with a closed loop metal bracket. I simple cut the loop with my saber saw with a hacksaw blade, pried the loop open, then installed the new hose within the open loop and squeezed it back shut with pliers to secure.
O'Reilly's offers two Ranger a/c hoses, one for most all engines and one for the 4.0 only. The 4.0 takes part# 55322.
Murray® Climate Control 55322 - Hose Assembly | O'Reilly Auto Parts