I tried searching for the answer but wasn't getting anywhere. Lately, I've noticed my temp gauge was always reading below normal, but everything seemed fine. I thought maybe I had a bad thermostat so I replaced it, and I had the same problem. Today while I was in line for food I noticed my temp gauge wasn't rising even after an hour of sitting in line. Also noticed that my heat wasn't warming up. I think my heater core is clogged, as I'm not losing any coolant. Is there something I can do to test my theory? I really can't afford to have a mechanic look at it. Thanks for any help. This is on a 2002 Taurus SES with the flex fuel engine.