[mgarblik]

I would buy or borrow a "real" flare nut wrench and it will come right out with a large pop. A Snap-On flare nut wrench will apply the load to the flats on the nut and not the sharp corners of the nut with it's flank drive design. They have a much larger cross section that surrounds the nut so it's very unlikely it will spread when you put the torque to it. Harbor freight, Crapsman, and other cheapies in this application should be called round off wrenches. I would estimate they are no better than 25% better than a regular open end wrench. If you need to save the line, that's the best way to go. One other option would be to go to the other end of the line and try to remove it there, such as the junction block. Then slide a quality box wrench, (preferably a 6-point), all the way up the line to the MC end and remove with the box wrench. Good luck.