I've not done this exact job; but, tubing nuts (the ones on each end of the steel line) are always turnable when new but corrosion sets in between the nut and the tube and the threads between the nut and the hose. Once the corrosion sets-in the tubing nuts seize. Penetrating oil, mild heat and patience will usually break the nuts loose but not always. I've seen lines crumble from the corrosion under the nut.

When working with those nuts, Kroil or PB Blaster a couple of days in advance can make a significant difference toward getting them loose. If the nuts are seized and you keep turning it pretzels the steel line to the point of ruin.

Kudos that you figured out a solution.

Good luck!!!

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