Will Hayes

Sounds like I will have to change the heater core. Thanks

I've flushed 3 times till water was clear, both hoses are the same temperature going into the heater core. Thanks for the help

Yes I have, it "feels" fine but is difficult to tell. When I turn it to the max there isn't any difference in heat. Remains the same Luke warm temperature.

Will give the borescope a try. Thanks for the reply.

Yes both hoses are the same temperature. (Has been flushed for good measure 3 times) The blend door actuator has been changed and the issue still persists.

I own a 2007 silverado 2500 (new style) has a 6.0L gas engine. I'm having trouble with the heat. It gets warm but never hot like it should be. I have flushed the coolant and the core 3 times, changed the blend door actuator and the thermostat. I can hear the actuator turning as I adjust the climate knob till about 1/2way onto the hot side then the motor seems to stop making a noise. (I suspect something maybe be blocking the actuator inside the vents?) When the air is in recirculation setting it warms up rapidly (1min or so) and works as it should. When changed back to outdoor air it cools back down. Not sure where to go from here, any help would be appreciated thank you!