White smoke almost always means water in the combustion chambers. Blue smoke means oil in the combustion chambers. Black smoke means carbon buildup in the combustion chambers.
Water can come from a number of places including a bad head gasket, a cracked head, cracked intake manifold, cracked block or condensation from sitting for a long time.
HotRod is right. Be careful about overpressure on the system. You could cause a problem you didn't have before.
