Sorry to open up a new thread on heat issues, but it seems every thread goes back to how to replace a front heater core (removing the dash) or replacing the back (taking off the trim panel in trunk).
I have a 2001 Durango 5.9L RT with the following symptoms: Front heater vents blow luke warm (the outermost by the window), the inner ones blow a little less warm (by the radio controls), while the rear vents blow completely cold.
I have removed the trim panel in the trunk and bought a new rear heater core, but I noticed both blend type doors moving ok (the forward one responds to the feet/upper vent selector ****, while the rear responds to the heat/cold selector). good, Since they both respond I don't think that is my problem. When I go to feel the hoses for the heater core however, they are both cold, I don't mind replacing the rear heater core because I bought a new one, but the fact that both supply and return are cold leads me to believe that the problem it's not my rear heater core, and neither are the blender doors since they both seem to work fine from one extreme to the next (stop to stop).
Today I topped off the coolant, thinking it may be low, which it was but still the same symptoms. I did however replace the water pump, thermostat and radiator about three years ago in the winter. I don't drive the car daily, since it is my wife's, but normally the temp gauge is just shy off the middle. She said it has always been that way, even before I replaced the water pump, thermostat and radiator. The only thing i can think off is that it might be my thermostat but i believe i bought whatever it called for (185 or 190 F). The hoses in the engine bay seem warm. Is there any valve(s) that can be stuck in the engine bay not giving me enough heat in the cab, whether that be front or rear heater cores?
Any help would be greatly appreciated.

 

There is an auxiliary electric water pump on 01-03 trucks. I wonder if that's acting up and affecting heater core flow.

 

Thank you That guy, I was tracing the heater lines in the engine bay the other day and I came across that pump, I just didn't know it was a pump because I didn't feel it vibrating or running. It was just under the windshield, on the left side of the engine bay, by the firewall. I will have to test it, but come to think of it I want to say the rubber line was warm on both ends. Once i check that pump, is there anything else in the way that could compromise the flow? The other scenario I was thinking prior to the electric pump, was that since both lines at the rear core were cold, could it be that the core is so clogged up that if there is absolutely no flow through the core, then the hot coolant the auxiliary pump is pushing can't reach the location where the core is in the rear of the car, which is where i touched the coolant lines?

 

I'm not actually sure how they plumbed the dual heater cores on the later trucks. There are probably diagrams in the FSMs. There are links to the FSMs towards the bottom of the DIY/FAQ section. https://dodgeforum.com/forum/1st-gen...ers-faq-s.html