It's the steering stop that's making the noise. It's a little metal peg that is supposed to be covered by a white plastic cap and when the cap either falls off or you wear a hole in it then the metal peg contacts the metal stop directly and you get that bad clicking noise. If you have just worn a hole in it you can pop that cap off, rotate it 180 degrees and put it back on and you should be good to go. If it's missing then it's junkyard time.