smoke comming out of air vents while air is on
by Visitor in Oswego, NY on April 05, 2010
Most likely your heater core is leaking. Turn the defroster vents on and see if the smoke leaves an oily residue on your front windshield. If yes, then it's coolant that is leaking out of the heater core and then turning into steam. You can bypass the heater core if you want, just get a radiator hose that can be cut to fit into a "U" shape. The only downside is that your car's heater won't work if you do this, so get a warm jacket to wear!!! Aside from the heater not working, bypassing the heater core usually won't cause any problems. Incidentally, replacing the heater core is an expensive fix, and a big pain to try and do yourself.