Mazda MPV Heater Heater Core

Heater Problem 2003 Mazda Mpv V6 Two Wheel Drive Automatic 45000 Miles I Think I Have A Bad Heatercore. Only When I Turn On The Heater...

I Can't Seem To Get Good Heat Out Of My Heater. I Had A Mechanic Flush The Core But It Still Doesn't Work. Also, There Is An Passenger...

Heater Does Not Blow Warm Air For A Long Time, Sometimes 30 -45 Minutes After Starting To Drive. Engine Temperature Gauge Goes To Normal...