I can't remove the cooler oil line from the radiator

Are you replacing the line or the radiator? If the line is being replaced, cut it off with an air cutoff tool, then use a deep six-point socket on that soft brass nut. Flare nut wrenches are made for those nuts too, often called "line wrenches". If you used an open end wrench you'd have been real lucky to get the nut loose without rounding it off.

As for rubber hose, pressures can get as high as 15 pounds if that is a transmission cooler line so regular fuel hose won't cut it. Use fuel injection hose and the special band-type clamps which will withstand much higher pressures. You also have to prepare the metal hose ends so the rubber hose won't push off. Simply clamping a rubber hose to a smooth metal pipe is not sufficient.

The secret is using the flare nut wrench. If the radiator is junk, try hammering the wrench onto the nut. Use a regular open end wrench on the larger nut for something to pull against. Keep in mind that if the nut is corroded that tight to the larger fitting, it's going to be rusted to the steel line too. If you can break it free from the fitting, you may be able to work it free on the line too instead of twisting the line.

Also, soak it with some penetrating oil. The Chrysler dealer's parts department has some real good stuff called "Rust Penetrant". It's black and sizzles. It will do in ten minutes what WD-40 will do in a weekend. I've heard good things about "PB Blaster" too but I haven't used it myself.

Did you get 'er handled?

THIS STUFF HERE---SPRAYED ONLY ON THE "LITTLE NUT" MAY "SHRINK" IT

(THIS WOULD SORTA BE THE OPPOSITE OF HEATING THE BIGGER NUT TO EXPAND IT. THE HEATING THING, DOES NOT LOOK LIKE AN OPTION)

COOLING THE ONE OR HEATING THE OTHER IS AN ATTEMPT TO MAKE THE MALE THREADS DISENGAGE FROM THE FEMALE THREADS

I HAVE USED THIS STUFF MYSELF---IT HAS WORKED PROBABLY 50% OF THE TIME ON MY PROJECTS. THE OLE AIR IN A CAN, THAT YOU DUST OFF YOUR COMPUTER, WHEN THE CAN IS TURNED UPSIDE DOWN AND SPRAYED, HAS THE SAME EFFECT THE PRODUCT IN MY PIC

SEE-UNS HOW YOU REALLY CANNOT SPRAY DIRECTLY ONTO THE THREADS

IF I WERE TRYING THIS METHOD ON YOUR SITUATION, MY ATTACK PLAN WOULD BE TO COVER THE LARGER NUT WITH A RAG OR SIMILAR ITEM, TAPE IT IN PLACE SO IT DOESN'T BLOW OFF.

THE IDEA IS NOT TO SHRINK THE BIGGER NUT (FEMALE THREADS). ONLY SHRINK THE MALE THREADS

IN ORDER TO GET THE "SUPER COLD" TO TRANSFER TO THE THREADS (WHERE IT IS NEEDED) YOU WILL REALLY HAVE TO "BLAST" THE EXPOSED PORTION REALLY GOOD

THIS STUFF IS REALLY COLD. ALMOST A COLD AS MY EX-WIFE. AND THAT IS COLD!

SO TAKE PRECAUTIONS TO PROTECT YOURSELF AND OTHERS. READ THE LABEL AND WEAR SAFETY GLASSES

IT'S AVAILABLE AT POPULAR PARTS STORES

THE MEDIC