I just drained a radiator to eliminate banging, but it didn't work as well
as I hoped. I also removed the valve and put some teflon around the stem,
because it leaked I see from a stain.

There was another radiator on this extension on the floor below, but it was
removed years ago. I haven't checked the valve. It's now inside a small
cabinet. I have to move it.

Could the pipe be clogged? The pipe system is undoubtably 70 years old.
Any thoughts?

John