White smoke

I just bought a mazda protege 1994, 200.000 miles. And when I start it, it has white smoke come from the catalic converter, and it comes up into the engine and out through the muffler. I dont know if I need a catalic converter or there is coolant in my exhaust. Or my head gasket is out. My friend says he thinks its the valve seals I really dont know about cars can u please help me. And it runs fine and the engine light does not come on. Thanks for your help.