I have PB Blasted, wrenched, dremmeled, and chissled away at the dang lower thermostat housing nut all day. It is now a mangled shredded piece of metal wrapped around the stud. I seriously think the last person to work on it may have used lock-tight or some other sealant on it. I have been thinking about trying to cut the engine-lift loop in half so I can try to crank it around and break the nuts seal. It is stuck tight and has never budged and I obviously now have now grip. I can get another 10mm nut to thread in on top of the stuck one, for what its worth. Any suggestions would be appreciated.