I found a leak on the radiator of my 1999 f-250 superduty where the upper plastic tank is crimped to the core. I've got 200,000 miles so I think a new radiator is in order. I want to do the job myself, but cannot loosen the transmission oil line closest to the drain **** of the radiator. The other line broke loose easily. I am unable to break the other lline loose using all my strength and a lot of penetrating oil. Any tips on this? The fitting is fairly soft and is beginning to round off. Is it possible that I may have to cut the line and patch in a piece? Anyone else have a problem like this?

 

Are you using flare nut wrenches to try and take it off? If it still won't go I'd use a very very small amount of heat on it to see if that will loosen it up. I remember mine were a PITA when I had to replace my radiator for the exact same reason. Also the new radiator will come with new adapters for the core so you can destroy them if need be.