1998 Dodge Durango no heat when using heater.

The heater core is blocked ! You can't have hot going in and cold coming out . The hot isn't going through ! How To Unclog Heater Core EricTheCarGuy

Hi Josh-
I assume that you have the proper mixture and levels of coolant in your radiator and plastic overflow tank. Open your radiator cap (when the engine is cold) to make sure this is the case. If not, fill as directed by your owners manual.
If the cooling system's thermostat is bad, the hot coolant coming from your engine can not circulate to the radiator in front of the car to dissipate this heat and return to the engine colder.
The odd part you describe is that cold air blows out of the heater. If your car is overheating, you should have above average heat, since your car is running hot.
A bad water pump may also prevent coolant from circulating correctly. Usually, a bad pump will show up as a puddle of coolant underneath your car-since the bearing or seals usually wear out on the pump. However, I've seen where the internal blades or impellers of the pump have worn out due to deposits in the coolant due to infrequent replacement.
Hope this helps!

Have you bled all the air out of the system? Assuming you have, I'm thinking you've still got a major blockage or more likely, because there's no pressure, you've got a bad water pump. The impeller can corrode or fail without actually leaking. There is also a shut off valve on the heater hose which may account for the lack of heat but not for the lack of pressure. I'd start with that and continue on. Please let me know how this worked and if I can help more if the problem persists. Thanks and good luck!

The heater core might need back flushed, I just did mine this winter. Go to dakota-durango.com and introduce your self and your rare as ever truck, a v6 durango, and have fun.

The blower has debris in it. It need to be remove and clean out. How do you remove the dash board. See no screws.

The rear vent system has a separate heater core/blower system. heater core could be plugged up or the coolant lines going to rear heater core are plugged. could also be low coolant/faulty water pump not producing enough pressure, or air in the cooling system which will need to be bled if so.

a bad heater core will just leak. it could leak alot. do you ever smell antifreeze? check the coolant level. it can get pretty low before it will overheat. the thermostat should be ok but there could be corrosion. when you had the water pump replaced was the cooling system flushed? 2001, its probably due for a flush. what coolant does it take? (green or orange)

The problem that has caused this cold air only issue is the Air Temerture Control Blend Door Actuator Motor, this motor is on the ouside of the air duct about center of the dash, in order to access and replace it u must remove the entire dash assembly. this is about a 12-15 hour job.

Heater control valve for the front unit is bad.

There is a valve located on one of the heater hoses that when you select heat moves to allow heated water to flow through the heater core. Yours is probably just stuck, with heat selected on the dash try to move valve by hand.