Why is water used as a coolant in the radiators of cars and why does it smell bad?

When water is pumped around a hot engine it gets very hot. It then goes into the top of the radiator and down the thin tubes to the bottom of the radiator. When the car is moving, or if the fan is spinning, the water in the radiators thin tubes is cooled. Then it goes back in the engine, heats up and the process repeats. The water will make the engine rust, so a corrosion inhibitor needs to be added to the water (usually in the form of antifreeze .) If it smells like poo the system probably needs draining and flushing out and then re-filling.