NO CAB HEATER despite replacement of components - Dodge Cummins Diesel Forum
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post #1 of 3 (permalink) Old 10-24-2018, 03:37 AM Thread Starter
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NO CAB HEATER despite replacement of components

Hi, I know this post has been beat to death but I have not found a solution, nor someone with the exact issue and steps taken.

I have a 2010 2500 6.7 cummins 4x4 with 151,000 miles

I have no heater in the cab as of last year.

I replaced water pump (along with serpentine belt) and thermostat (190*). I drained and flushed the coolant and added new coolant based off the forums recommendations of the HOAT Zerex G-05.

While i had the coolant drained I tried to run water from a water hose through the heater core by disconnecting both rubber lines near firewall and running water through them. I will admit, it did not flow as easy as I think it should, but then again I did not have a solid way of connecting water with a tight connection. It was basically holding water hose up against rubber hose. Because the flow seemed low I used a funnel to slowly poor a container of CLR in heater core. My thought process was to do this to clean out/flush core. After letting sit a few minutes (even though the CLR immediately flowed through albeit slowly) I flushed lots of water through the core.

I then re-added coolant (recommended 22 quartz)..turned heater on wide open, ran truck on high idle up to temp and finally got it up to 194* coolant temp but still no heater in cab. I also used the allen/hex nut on top of engine near EGR/thermostat to bleed coolant lines.

I do not think it is the blend doors because I can hear the blend doors flopping open/close when I cycle heat on off. I have dual climate control. Based on my understanding of the hvac system and how air is routed I would think I would at least have heat on one side if it was a blend door issue. Right or wrong? Odds of both driver and passenger blend door /blend door motor going out at same time would have to be next to impossible right? Plus I can hear them flopping.

I have read about air bubble in heater core. A) how common is this? B) Can a little pocket of air really hold back 200 degree coolant even if I am using the bleed line to bleed air? C) This problem started long before i replaced water pump, thermostat, or coolant, so could an air bubble just happen seemingly overnight?

If it is an air bubble in the heater core, how can I clear it?

Any thoughts or suggestions? Are there any other temperature sensors or culprits I may be overlooking?
How easily should water from a water hose be able to flow though a heater core?

Any thoughts and experiences would be greatly appreciated. THANKS!

PS if it matters I have an H&S tuner with tranny tune, and cat back exhaust with deletes of everything but muffler. I have stock EGR equipment in place but have the EGR turned "off" in the H&S settings.

2010 Dodge Ram 2500 Laramie 4x4. 4.5" tuff country lift.

Last edited by Musicpro4x4; 10-24-2018 at 03:42 AM. Reason: Added info.
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post #2 of 3 (permalink) Old 10-24-2018, 05:02 PM
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The heater core should flow quite readily. When working properly, the coolant line going into the heater should be hot, and the other return line cold. When the core starts to clog, the line going in can be not as hot as it loses heat by the time it reaches the heater as the coolant is flowing so slowly, or the return line can be warm still as well as the coolant only flows through a small part of the core.

I dealt with this on my '02 1500. I also changed the blend doors to aftermarket metal ones while I was in there. The blend doors could be broken or warped not properly directing airflow.

2017 6.7L Ram 2500 Laramie Crew Cab Granite Crystal Sport Appearance Group, 68RFE, rear air suspension
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post #3 of 3 (permalink) Old 10-25-2018, 02:09 AM
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Im dealing with a similar issue on the 2011 I purchased a few weeks ago so i will run through what i have done so far.

First thing i noticed was the lack of high airflow coming from the vents and passenger side was slightly warmer, so i removed the blower motor and inspected the evap coil, it was totally caked up with black gunk (220k on odometer). Took a water hose to the EVAP coil the best i could (nozzle was too big and i could not remove it so i know i didnt get it as clean as i could have and have done in other vehicles) Spray some, let it drain out and spray again. Drivers side heat is furthest side from firewall and actuator motor can be seen when you remove the glove box. I got a noticeable amount of higher air flow and slightly warmer heat after this, but still not hot.

While i was down there and things were drying, checked the operation of the driver side heat door. Seemed to operate at full range of motion, removed motor and inspected for stripped gears. Manually moved door to ensure it was actually moving and not broken. Appeared to be operable.

Took IR gun to heater lines, 119 on supply and 108 on return. Let engine cool and gave a more through look at the coolant. The coolant looked really orange like DexCool. Having not known the previous mx history i felt it was best to drain and flush the system and start fresh with new G05 and previous owner may have mixed coolants. Drained system, noticed a significant amount of crystallized sediment while draining system. Drained and refilled with distilled water 3 times and still had sediments. Due to time constraints, i refilled system with coolant and got mixture to 50/50 ratio. After the system burped, the heat was warmer but still not what is expected.

Let it sit over night. Removed heater lines and placed ziplock baggies over engine side connections. Hooked up some spare 5/8 hose to heater core lines. Back washed core, forced water from return line (going to turbo) and forced out a large amount of crystallized substances from the core. Purged with air and reversed the water flow, then purged with air in the core again and back washed. Did that several times. Blew out the hose water one last time then flushed with distilled water and purged with air again. Reconnected supply hose and started truck for a few seconds until coolant came out return line. Turned truck off and reconnected return line to turbo. Went for a drive to check my lottery tickets (not a winner) and let the system burp. I now had much much better heat and i now fill confidant that we will not freeze in the winter now.

After research, the crystallized sediment appears to be from hard water minerals, more than likely previous owner used tap water when they filled the system with dexcool or what ever coolant they used. Im not sure if that will help you any but its worth a shot. Took about 3gal of full strength g05 and about 12gal of distilled water. Later on i will attempt to spray out the evap coil again with a different nozzle that i can get closer to the coil and hopefully penetrate and clean out the heater core some, if not i may remove the dash for a through cleaning in the spring/summer. Cabin air filter mod is also in the future to help keep the air system clean, ive done that on all my previous rams and is well worth it.

2011 CC non-HO
2014/2015 Ecodiesel GDE Tuned--Sold & 2007 5.9 MEGAcab w/Edge Evolution--Sold
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