I did have trouble with the green protective coating. For some reason I sanded on them, "gooed" it up and the nut would not rotate and so on. Took them back for new ones and didn't touch the coating. Worked well. Do you have leaks at where the City Auto Parts line meets Napa line? Could be the Napa coated ones. Anyway, you do have to retighten sometimes to stop leaks. Just don't mess with that coating or it will contaminate the threads and it will "goo" into space between nut and tube. It's not just paint, it's epoxy coating or plastic coating or ?? Take a known SAE male and female thread with you to test each end of each piece you buy.

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