My 99 Durango won't really heat up, even after an hour it won't blow hot air. If i turn the blowers off and give it about 5 minutes and then turn them on and it blow hot air for a couple seconds. I just flushed the entire cooling system and got all the gunk out. I don't know if it would be the heater core or just the thermostat being stuck open and needing replacing. Thanks.

 

the thermostat could be the issue as well as the heater core but, what motor do you have?

 

what does the engine temp gauge look like? Is the engine getting hot but the heater core not?

Also when the engine is warn under the hood if you grab the heater core hoses are one or both hot?

 

I ran across the same issue , Here is what I did. Check the heater hoses with the engine warm. Is one much warmer than the other? if it is it could be a clogged up heater core restricting the flow of hot water. I simply hooked a garden hose up to the return heater hose ( the cooler of the 2 hoses) and ran water backwards through the heater core. Alot of sediment and crap flowed out and now it gets nice and warm. youtube backflush heater core.

 

I have tryed everything to get heat. New heater core, new water pump, flushed core. 5.9 , heat gage 190, I haven' had good heat since I purcosed it new in 2000. Still little heat.