Big Goverment has its head in the tent on this one. It is against Federal law to add freon (of any kind) to a system that is known to ber leaking. The only legal method is to add enough refrigerant to find theleak, evacuate AND RECOVER all the refrigerant, and fix the leak.

Now, there ARE refrigerants (not freons), that are ok to use in leaking systems since they do not attack the ozone layer.

I have heard some good reports on CRYOSEAL also. If I had a leaking evaporator, I would try Cryoseal first.