Does it do this on start up when the motor is cold ? If so it isn't steam b/c the motor isn't hot enough to create steam. Have you got under it to see if there is any coolant anywhere? Mine didn't really have any "noticeable " leaks until you looked under it. It was so slow that it would take a while to notice a drop in coolant. When I took the radiator out I couldn't believe it was still in one piece.
9er, 3.5 IRO lift + 3/4" spacers w/ adjustable trac bars and arms, 242 swap, 285/70/17 Duratracs and some other doo dads