Well, my expansion valve is leaking again (second time in less than a year). The AC system works great when is full of freon. It seems that the leak comes from the front of the valve. I have the dye in the system so, it is very obvious. I changed the o-rings and also a new expansion valve was installed. Vacuum , flush, etc. The question: how tight (or loose) do the fittings in this valve need to be? torque values? I still have the R12. Is there a sealing compound that I can use?