taurus water pump test?

How do I test water pump for sufficient pressure? - quality of vanes present , for proper flow to the heater core. 1999 ford taurus has no heat, at 90,000 miles. Pinching the bypass heater hose allows some heat inside car. Looks like flow problem. temp gauge reads normal.Inlet and outlet hose of heater core is different temperature. The motor for blender door turns forward and backward by sound. Thermostat was changed on engine, along with the rusted steel piping on firewall. Heater core was flushed once at garage. It's -5 degrees here in New York.

Does the engine temp get too hot, or fluctuate? if not i wouldn't point toward the pump. I read a thread here that a guy tested the capacity of his heater core compared to a new one. Here is the thread: http://www.automotiveforums.com/vbulletin/showthread.php?t=326492. Something else to consider.

The only "failure" I have ever seen in an engine water pump is the seal on the shaft. The unit has no contact parts other than the bearing and seal. If your pump isn't leaking is probably OK.