heater not working..
2001 F150 4.2 V6 heater not blowing hot air. does blow hot air for a few seconds, but then no more heat. turn off the heater and try again in a few minutes and again get a blast of hot air then it cools again. one of the hoses going to the heater core is significantly hotter than the other. backflushed the system and water is passing thru, but only about a 0.25" stream is coming out. am currently running flush thru the system. could it just be that the heater core is plugged...