Cooling water loss in running climate...

Hello V8 friends
In the hot days when I was constantly riding with climate, I had to go every 2 days about. Re-dip 1 litre of cooling water. If I drive without, the cooling water level remains constant. In the footroom passenger side has collected a lot of cooling water(?). I was diagnosed with defective heat exchangers. Can it have other causes and if not, what is the cost of changing the heat exchanger?
With best thanks in advance, Frank