by Pete in NH » Sat Jun 21, 2014 2:43 pm
Hi,
Those things can be very difficult to get apart. I would try brushing as much of the rust from the threads as you can with a small wire brush as a first step. Then I would try getting something like PB Blaster solvent on the threads a little bit at a time and letting it soak in well. I would get a few drops of solvent on it every day, twice day for several days. Then try to turn it with a wrench on the coupling nut. If it begins to turn I would try to work a few more drops of solvent in it by working the nut back and forth until the solvent really gets in there.
Patience is the key when working on something like this. Being in a hurry often gets you some broken parts. Good luck!