I don't think the end caps are iron, they should be cast aluminum. I recall that there was a rivet or screw on the bottom of the crossbar as well, so you might be missing that one. once you have made sure you have all the rivets completely drilled out, you just have to tap the end cap off with a flat head screw driver. If it has corroded and you can't get it off, you may have to break it off and get another.