1994 Ford Taurus Radiator Leak - Upper

I can't figure out why the radiator is leaking from the top of the radiator, on the opposite side of the fill cap. I put a bottle of Prestone anti-leak with pellets in yesterday to prevent a tiny, almost unidentifiable leak from becoming a large one. Instead, the opposite happened! I broke up and dissolved the pellets as best as possible. Yet I am losing large amounts of coolant now and the spillage is casuing smoke to pout from the engine. As yet, I have not noticed the car actually overheating, but it likely will. What is going on? Please help!!!!!