I have a 1998 Dodge Ram 1500 2wd w/ 5.9l., I have flushed the entire cooling system. I am running at about 190-195 consistently. Took the glove box out and the heater core is very very hot yet i cannot get the heat that it should be. Both the heater hoses are very hot hot. Dodge dealer said the mixer door is probably the problem, but wants 400= to fix it. Is there any way to find out if that is the real problem and should i leave it to the pros to fix? Please help me! Winter is fast approaching and i need my heat! Thank you, Robert
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Two likely possiblities: lazy thermostat (can be easily diagnosed with a scan tool) or a restricted heater core due to lack of cooling system maintenance (was it flushed at 50,000 miles?). Could also be a HVAC mode door not moving to the full hot position.
Do the two heater core supply hoses get hot where they go through the firewall to the heater core? If one is hot the other cool to the touch then you have a plugged heater core flush it out with a garden hose, if they are both hot then a part called the air temperature control blend door is not moving inside the air ducting due to it being warped and jammed and/or the actuator that moves it being defective, to replace the blend door and its actuator requires the dash be removed from the truck to access the air ducting that contains the blend door.
You probably have a restricted heater core. Buy a can of radiator flush and follow the directions on the can. If this doesn't work, then take both heater hoses loose at the engine an run water thru the heater hose with a garden hose. Hopefully this will clear the restriction.
Hope this helps :)
I just bought a 98 with a 360 and it has the same problem. If I rev mine up or drive in Drive not Overdrive the heat gets alot better. I talked to a service manager at a Dodge dealer and he told me the most likely problem is the heater core is plugged with casting sand that comes off the engine block over time. I flushed it twice with some improvement but I still think it needs another one or two times to make it better yet. There was alot of gunk that came out, and the second flush I caught a sample earlier then I did on the first flush and once it settled you can see there is actual sand in it.
First check your radiator cap to make sure theres no pressure escaping. The cooling system needs pressure to push the hot water to the heater core. You also need to look at your heater core itself. With the engine running touch the lines coming in to the heater core through the firewall. If they're both hot you may need to replace the core, if only one is hot you've got a blockage in the cooling system preventing the flow to the heater core.
you need to get under the dash board and remove the passenger lower kick panel. ther will be a small motor bolted into the evaporator housing. remove it and manually move the blend door. if the heat gets hot the you need a blend door actuator.
circulation of hot hot water to inside cabin to heater core ..and fan blowing strong are all necessary here.....back flush system.. (good cooling system service) including flushing teh heater lines with all heater lines open ...refill and test... or to be sure replace thermostat and any suspect heater hoses at same time....a good shop with infrared gun can trace heat and locate blockage if necessary... good luck