Vice grip sells pliers made to fit a hex nut, I find that they work great for tube nuts that even a flare nut wrench won't loosen. You can get them at most any good hardware or home improvement store.

You may end up having to replace the hard line, don't take any chances with brakes.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-