That is a good question. However, if both heater core hoses are hot, then the coolant is flowing through the heater core and should produce heat unless there is something stopping it from coming into the vehicle. The only thing left is the blend door. As far as the RPM's, you are forcing coolant through the system faster (hotter). If you didn't tell me both heater core hoses were hot, I would question an air block, but that wouldn't make sense now.
Tuesday, January 18th, 2011 AT 9:33 PM