A condenser column would need to be cooled. Even a passive radiator adds weight. Another step in the engine cycle can cool and condense the water vapor to liq

A condenser column would need to be cooled. Even a passive radiator adds weight. Another step in the engine cycle can cool and condense the water vapor to liquid, and extract additional energy from the exhaust. The weight of the required additional engine parts, and the cooler in particular, tends to erase all the actual benefit in an automobile. Cargo ships and train locomotives could do it.