So how is the water pump getting fluid past the thermostat when everything is cold? I'm used to domestic V-8's where the thermostat is on the top of the intake for the radiator return line. This Mazdaspeed 6 I'm working on has the t-stat on pump suction. I have the engine full and a new metal impeller pump, with corksport throttle body, so that is not cooled.
Is it possible to get a new water pump with opposite rotation by mistake for this engine?
I am running this engine on a test stand with a head tank for coolant reservoir. The tank is 5 gallon and is high enough so that both radiator lines are underwater. And not getting flow after the temp gauge shows engine is warm enough.