[Mike Noc]

Originally Posted by kaiser

It does create pressure, connect a hose to the outlet, and see the water rise. The higher it rises, the higher the pressure. However, there is a limit to the pressure, and it is rather low, after which it will just trash the water.
Compare that to a positive displacement (gear/piston etc) pump. Here you will have pressure of a nature that the jet can shoot through you hand, or crack a cylinder or bend a conrod!

The thermostat in the Diesel will have nothing to do with pressure would be my thinking.

Well the smaller disc valve appears to be opening to prevent any increase in both pressure and flow rates when the thermostat is closed and the coolant is only using the smaller heater matrix pipework.

Mike