It's a common problem when removing oil lines from the external thermostat. The aluminum thermostat threads become fused to the steel tube nut that secures the oil lines. If you get enough leverage to force the nut free, it takes the aluminum threads along with it - destroying the expensive thermostat and the oil line.
Elephant Racing has the solution; we are manufacturing a 30mm tube nut replacement kit that let's you save thermostats and oil lines. If your oil lines won't come free from the thermostat, use a cut-off wheel to slit the side of the tube nut. You can then break the nut free using a cold chisel. This technique sacrifices the tube nut to save the expensive thermostat.
You then use our kit to replace the tube nut that was cut off. Both the oil line and the thermostat are saved.
The kit provides a 2-piece tube nut. The threaded nut fits over the end of the tube and is slipped on first. A spring lock ring is then slipped on. The spring lock ring cinches down on the tube, preventing the nut from coming off.
Kit Installed on Oil Line