Transmission cooler lines - are they pressurized?

[OldRedFord]

You can use a compression union on steel line?

[70_F100]

You can use a compression union on steel line?

You can try it.

I've never had much luck with compression fittings on steel tubing.

Generally, they are all double-flared.

[gleno]

This may be an older post, but the tip is apropos to many situations of stuck or frozen fastenings in general. I have found that heat can be my friend when breaking apart stubborn metal -to-metal connections, whether it is a 2" iron pipe nipple on a plumbing job or a stuck rocker arm stud in a cylinder head.

The approach I use is always surgical and cautious, but properly applied heat to a stubborn connection usually prevails without bloody knuckles. I like my propane torch, used gently, and in the case above, being aware that the solder in the radiator flows at somewhere near 600 degrees, F. , so care must be taken to isolate the heat near the problem connection, to avoid separating the lower tank of the radiator from the core. Just "sting it a little", be gentle with the torque force, and good things usually happen.