Steam cars lost out to gasoline engines because of the water problem --they couldn't build radiators good enough to condense all the water that had been turned to steam (after the steam had expanded in the engine). So they had to frequently fill a water tank, in addition to filling a fuel tank. Today, we might be able to build efficient-enough radiators, especially if we go the route of making only 20 HP steam engines in conjunction with something that allows rapid acceleration and storage of regenerative-braking energy, as described in prior posts. You make a 150 HP steam engine for a car even today, and you, too, will probably have to add water at regular intervals. And then there is the efficiency problem, in that car-sized steam engines are probably only/roughly 40% efficient (the steam engines in large power plants manage 50% efficiency partly because of size-scaling). Better things are available, for cars.