Just got a question about my beater Mazda. My heat doesn't work, and its cold like in the teens all the time, you can see my problem. I changed the thermostat, cleaned out the hoses, my radiator is full. I dunno what it is, when RPM's go higher its a little better. Could it be the water pump, but if so wouldn't my engine temp be a little higher? But its not. Any hints, thanks.

 

I would think it'd be a heater core problem.