whats the deal on a 98 durango heater core? mine at best blows cool air, I've never had a leak on the inside and have change my thermostat 3 times

 

It boils down to 2 things, either the heater core is plugged with sludge, or there is a blend door issue. The door is mechanically controlled via cable from temp dial that changes flow between A/C coil and heater core. There are two hoses that feed the heater core through the firewall nearer the driver side. The feed is off the water pump, the return dumps into the top of the manifold. Are both these hoses hot? If they are, then probably blend door. If not, heater core is the issue. To verify your blend door is working try this. Get the truck up to temp, turn the fan on high and rotate the temp dial lock to lock a couple of times. You should feel a temp difference and hear a slight change in the flow.

You can try to flush the core by removing the hoses and using a garden hose. Flush it both ways. This would also be a good time to flush the entire cooling system, if your heater core is plugged you probably have more gunk in the system that could stand to be flushed.

You title says it all, if flushing doesn't work, your dash is coming out. You also need to pull the dash to get to the blend door. Thank you Dodge engineers!

 

yup +1 on all of that sorry man if a flush doesnt fix it, your pulling the dash

 

use the water hose both ways on the heater hoses. if the heater hoses are really stuck on the heater pipes, and don't want to come off, you can just cut the hoses out in a convenient place, and resplice them with sleeves and clamps when you're done.

if the garden hose backflush doesn't help, you might try prestone or similar chemical flush. its designed to break loose scale and might help. i was thinking i would try it if it ever gets up out of deep freeze temps.

 

also make sure you are full of coolant. yuor rad might be but the heater core might not be. try bleeding the system . its kind of a PITA.