It's possible that these two issues could be related to a faulty heater core that could be leaking radiator fluid. The steam you are seeing from your Jeep Grand Cherokee's dash could be related to condensation in your heating and air conditioning system. Does the steam smell sweet, like anti-freeze? Are you seeing any fluid leaking into the passenger compartment or under the vehicle?
I found the following discussion online at the Cherokee forums, and it might provide some clues about your problem: http://www.cherokeeforum.com/f2/steam-defrost-vents-82712/
For additional assistance, please find an AskPatty Certified Repair Shop at http://www.askpatty.com/search/?type=all&m=30&q=&keyword= and they can help you diagnose and repair the problem.