I always thought white smoke out the tailpipe meant you've blown your head gasket. If it is blown, you'll have a distended, bloated, rock hard, radiator hose, and after cooling down you'll lose all your pressure in your cooling system.

Can't do it gracefully with the whatever they call it degas bottle, the reservoir, but on radiators with a cap you would leave the cap off and let the engine warm up and look for white bubbles in the coolant.