My wager is that it is a threaded pipe, and you're not catching the 'threads' with your turns or the threaded portion is locked in and merely the stem is turning. Since you tried cold, I would move to gentle heat and see if you can loosen up the goo holding the threaded portion in place. With some constant tension on the stem, you may be able to get it to stick enough to twist the threaded portion out. Also since you'll be restoring it, perhaps some PB blaster or other penetrating oil will be of some assistance.