I replaced my thermostat housing because it was leaking. I had to find out where the leak was. So I plugged up all six hose connections and drilled a steel plate to cover the block connection and allow an air line connection. Ran 20 pounds of air pressure. The entire assembly was put underwater in a laundry tub. I was surprised that the leak was not one of the seams but a very small pin hole or crack in the housing. The arrow in the picture points to the general area. The leak was actually in the corner. Again, I was surprised that my housing did not leak where they were joined together. Anyone else pressure test their housing?