What could cause white smoke to come out of the exhaust of a 1989 240sx?

What could cause white smoke to come out of the exhaust of a 1989 240sx?
White smoke from the exhaust is a sign of coolant entering the combustion chamber. Usually a blown head gasket or cracked head. STOP driving the car immediately. Severe engine damage will occur if you continue to run this engine.Sounds like steam......you may be getting coolant into the combustion chamber.