Originally Posted by Chad300tdt

The only way to be sure to not damage the threads on the cooler is to cut the fittings off the cooler lines with a dremel tool.

Cut a perpendicular slot on the nut so you can use a screwdriver to pry the nut open and off the threads.

I cut the lines off and remove the cooler so I can cut the fittings off at my bench.

The first time I replaced cooler lines I tried penetrating oil and heat while being VERY careful, but the threads were still slightly galled. Since then I cut the fittings off, and the threads are always perfect.