Nope--no shutoff valves in the hoses. I would have suspected the heat exchanger inside the Raritan, except for the fact that I have a diesel-fired hydronic heater plumbed into the engine coolant lines and, using it alone, it heats the Raritan like it always has for the last 12 years. A diesel mechanic and I troubleshot the system yesterday and verified that the engine thermostat is working, the coolant lines all heat up like they should and the coolant line to the overflow tank heats up. It may be that there is a restriction near (or in) the Raritan that is overcome by the two in-line water pumps that are part of the hydronic heat system--whereas the engine pump alone won't do it. So--I'm going to try running the engine until the lines are hot, confirming that I'm not getting hot water at the tap, and then turning on the hydronic heater (air only, no furnace function, which turns on the two pumps) and see if that allows the Raritan to heat up.... Let you know.