Confirming the posts above, it's likely your heater core. I had a Buick Skyhawk back in college that would break the passengerside motormount. When the engine torqued, it would tug on the hoses to the heater core causing the stems going into the core to snap at the weld. Sticky windshield film, smell of antifreeze, and a puddle on the passengerside floormat. I broke mounts and heater cores with regularity - got pretty good at doing things by feel (motor mounts) and on the fly with the heatercore. Like my fellow colleagues above, things seem to break on the coldest day of the winter! You might be able to grit it out for a few days to line up the time you need to do the job yourself. Keep a short handled scraper for the inside of the windshield and if you can, connect the input hose to the output hose to bypass the heater core althogether (I would use the broken stem for the bypass slipping it into the return hose and clamping off). Either find a buddy's garage you can borrow if you don't have your own, or contemplate a cold trip to see duhkrafties in Michigan. Good Luck!!