2003 tahoe rear AC leak. Please look and help.

[aquacure]

Been losing my refrigerant every 3-4 days. Finally found this at the rear AC behind the back passenger tire. This pic shows what happens when I sprayed it with soapy water. Large leak, big bubbles right away. It's not the connections, the bubbles are coming from the top of the large block the lines are going into. Appears to go up into the floor where the rear ac is located. Is there some large oring in there or something? The rear ac hasn't even been working, I was assuming it was the rear expansion valve after I had already checked the blend door. If I have to take all this apart I guess it would be a good time to put this in.
Does anybody have an idea of what I'm in for? Specifically with sealing up this leak. Thanks in advance. New owner here and havn't posted on a forum in a long time so I apologize if this is sloppy.

 

[sumo]

pain in the but. You can get rear block off kits where you'll only have front ac

 

[AH64Medic]

There are nuts up there holding those lines to the evaporator inside the fender area. Try seeing if they are loose first. I can't remember but I think there are two o-rings where those two lines mate with the evaporator lines. It may just be loose and need to be tightened. But... You'll have to discharge the refrigerant and get a new dryer/accumulator and pull a vacuum before putting in new refrigerant. The system is closed and now that it is leaking, air and moisture are bound to be in the lines. Might as well replace the orifice and expansion while you are at it. Not a hard job and not too expensive.