Does the Water Pump "Dead Head" when the Thermostat is closed? If so, isn't that bad for the pump?

Forgive my stupidity for not knowing the term 'dead head' (I'm assuming it means restricted flow from the context of the question) but, the water pump itself doesn't make water pressure (like a true fluid pump would). The pressure in a cooling system is caused by the temperature rise of the coolant, not the pump.

The coolant, thermostat open or not, is still routed to the heater core and back to the radiator allowing the pump to still move water.

Maybe I (nor others) am not understanding the question ?

You answered. If I understand it. I think what was meant by "dead head"-pumping against itself with no where for the coolant to go could cause the pump to fight a no-win battle without flow..?..
So with the flow going thru the heater core,there IS movement. There are quite a few heater deletes in TGO so I don't think it's a problem.

Sorry to confuse, I thought this was a common term, but you are correct with your interpretation. What I mean is; If the theromostat is closed, does the water pump still have a water flow path?

You say that the heater core is still an open path, but isn't that only when the heater is turned ON from the control panel in the dash? (Isn't that what the Diverter Valve does, route water to the core?) And what about the folks that have disconnected the heater core from the water system?

It just seems to me that the water pump NEEDS to have a flow path at all times in order to keep from being damaged.