White smoke from the exhaust of a car usually means that coolant is getting into the combustion chambers of the engine. This can happen because of a cracked or leaking head gasket, which allows coolant to seep into the cylinders. In extreme cases, the head gasket may need to be replaced. White smoke could also be steam caused by condensation in the exhaust pipe. However, excessive amounts of white smoke could indicate head gasket failure. It is important to address this issue as soon as possible to prevent further damage to the engine.