O.K., I've replaced the impeller which had a number of broken blades, I located and removed all the missing blades (an more!) from the heat exchanger, I removed the heat exchanger and had it acid cleaned since there were plenty of clogged tubes, I removed and replaced the thermostat, and still the engine runs hot (about 200-210). I also removed the thermostat entirely and ran the engine and the temperature never got above 122, so I figured that told me the thermostat was the problem, but a new thermostat did not fix things. What can I do next?????