Heat is not blowing hot (a little more complicated than you may think)


Latimera

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As the title says, the heat in my 2006 Wrangler TJ is not blowing hot. This started to happen after I replaced the heater core. I want to be as thorough as I can with this post so here is a rundown of everything leading up to this moment.

My TJ had a leaky heater core, but the heat still blew super-hot. I tore the dash apart and decided it was a good idea to replace most of the hard to get to parts in the heater box to avoid having to take it all apart again in the future. The parts replaced were the heater core, AC core, blower motor assembly, blower motor resistor, AC line O-rings, and AC accumulator. After getting her all back together I noticed the heat no longer blew hot. It was now blowing room temperature. I then proceeded to top off the coolant and pull a vacuum to get rid of any air pockets in the system. Still Nothing. I then replaced the thermostat and thermostat gasket thinking it might be that, with no luck. I then checked all the doors on the heater box from the outside and they seem to be functioning fine. I took the electric motor off of the blend door and was able to feel it fully open and fully close when I moved it with my hand. I parked the Jeep on a steep incline hoping any air bubbles would rise to the top and come out the radiator cap, added a bit more coolant and still nothing. I then disconnected the two heater hose lines from the core in the firewall and coolant came pouring out, indicating there is no air pocket in the core. The water pump was replaced about 2 years ago, so I don’t think it’s that.

Other important information is that when I rev the Jeep up either when driving or still it will blow hot for a second or two then return to cold/room temperature. When I turn the center hot/cold climate knob to cold the air does blow colder, just when I turn it to heat it is not hot. So, I think that it is working fine. I am using MOPAR coolant mixed to about 70% coolant 30% distilled water. I am at a complete loss here now and don’t know what to do. Looking for any advice at all and thank you in advance!

Parts Replaced:
Heater Core
AC Core
Blower motor assembly
Blower motor resistor
AC line O-rings
AC accumulator
Thermostat
Thermostat gasket
Coolant added multiple times

Jeep:
2006 Wrangler TJ Sport 4.0 with AC/Heat

TLDR:
Heat is not blowing hot after replacing all the parts listed above. Can’t think of anything else it could be. Plz help.
 

Claytone

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Centennial, CO
Will it blow hot if you keep the rpm up? If so then it sounds like air in the system.
How many full hot and full cold cycles has the engine gone thru? It may take a few to evacuate all the air.
 
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Latimera

Latimera

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If I hold it almost at the redline it will stay hot while under load. As soon as I let off or lower it to 2-3000 rpm it will go cold again. As for hot cold cycles id say its been at least 10-15 by now. I really cant see it being air after all ive done, but at the same time thats all that really makes sense.
 

MountaineerTom

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Do you know the brand heater core?

@BigWidd had a similar problem with an after market heater core recently.

 

Claytone

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Centennial, CO
Yeah that is weird, the couple of times I’ve had my system open it took much less than that to get the air out.
There have been a few folks on here with new restricted heater cores. Do a search and see.

Edit, ^^ beat me to it.
 
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Latimera

Latimera

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Do you know the brand heater core?

@BigWidd had a similar problem with an after market heater core recently.

The heater core is this one from Rock Auto, I just breifly read through that thread you linked and it seems very similar to my issue. Seems like a strong possibilty I got a bad core, but I wanna avoid taking that dash apart again at all costs so I will wait for a few more replies before I dive into that. Do you know of a better/working heater core you would reccomend?
 

MountaineerTom

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The heater core is this one from Rock Auto, I just breifly read through that thread you linked and it seems very similar to my issue. Seems like a strong possibilty I got a bad core, but I wanna avoid taking that dash apart again at all costs so I will wait for a few more replies before I dive into that. Do you know of a better/working heater core you would reccomend?
I don’t blame you. I changed my core almost 3 years ago and I wouldn’t have wanted to do it back-to-back.

I used a MOPAR core.
 
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Latimera

Latimera

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Huge shoutout to @MountaineerTom for linking that thread with someone who had a similar issue. After reading through that thread I found this one where I came across the picture below. This shows the plastic "turbulators" used in the aftermarket heater core vs the metal ones in the stock. Notice how the OEM metal ones are long, thin, and have less spirals while the aftermarket plastic ones are thicker with more spirals. Based on my research, @BigWidd 's post, and @Jeffrey Hamre 's picture, I have come to the conclusion that my aftermarket core uses these plastic "turbulators" that restrict the coolant flow too much resulting in cool air at idle.

Tomorrow I will check to see if I still have my stock and cut it open to confirm it has metal "turbulators", if it does I will then start the dissasembly process again and cut open the new core to see if they are plastic. Best part about this though is that after calling the Jeep dealership today I found out they discontinued my core 4 days ago, and there are none available anywhere in the US. I found one on mopar parts website that is $350. So I will have to resort to the OMIX one on Extreme Terrain which seems to have the best reviews of any I have found.

I dont know when I will have the time to get the new new heater core installed but I will at least be able to confirm if the OEM one has metal spirals tomorrow, and confirm if the aftermarket one is palstic by the end of the weekend. I will then upload a new thread detailing the entire process once I get a new new core isntalled and working. I want to make sure NO ONE ever runs into this issue in the future becasue it is a huge pain.
Screen Shot 2021-01-18 at 8.11.31 PM.png
Screen Shot 2021-01-18 at 8.11.54 PM.png
 
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MountaineerTom

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Huge shoutout to @MountaineerTom for linking that thread with someone who had a similar issue. After reading through that thread I found this one where I came across the picture below. This shows the plastic "turbulators" used in the aftermarket heater core vs the metal ones in the stock. Notice how the OEM metal ones are long, thin, and have less spirals while the aftermarket plastic ones are thicker with more spirals. Based on my research, @BigWidd 's post, and @Jeffrey Hamre 's picture, I have come to the conclusion that my aftermarket core uses these plastic "turbulators" that restrict the coolant flow too much resulting in cool air at idle.

Tomorrow I will check to see if I still have my stock and cut it open to confirm it has metal "turbulators", if it does I will then start the dissasembly process again and cut open the new core to see if they are plastic. Best part about this though is that after calling the Jeep dealership today I found out they discontinued my core 4 days ago, and there are none available anywhere in the US. I found one on mopar parts website that is $350. So I will have to resort to the OMIX one on Extreme Terrain which seems to have the best reviews of any I have found.

I dont know when I will have the time to get the new new heater core installed but I will at least be able to confirm if the OEM one has metal spirals tomorrow, and confirm if the aftermarket one is palstic by the end of the weekend. I will then upload a new thread detailing the entire process once I get a new new core isntalled and working. I want to make sure NO ONE ever runs into this issue in the future becasue it is a huge pain. View attachment 219167View attachment 219168

I‘m going to tag @Mr. Bills in this. I think it was him that found a seemingly good replacement core for a good price.

I never can remember the brand or website.
 
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Latimera

Latimera

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So I cut open the stock heater core tody and can confirm the use of long, thin, metal turbulators. Next step will be to take apart the new core and see if they use plastic thicker ones like I suspect. Dont know when I will get around to it but I will update this thread when I do. Below you can see the turbulators I pulled from the stock core. They are long and thin making it so coolant can flow easily and freely. My guess is that the aftermarket one uses plastic thicker ones that restrict flow like in the case of @BigWidd 's.
IMG_6209.jpeg
IMG_6210.jpeg
 
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qslim

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This is a great thread, I have the heater core / evaporator on the list for winter upgrades and don't want to go through this myself. Plus I learned what a turbulator is.
 
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Latimera

Latimera

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Hey all, just got the new core from performance radiator installed today and the heat blows hotter than ever. I will be posting a new thread about everything that happened and what I learned from it to make sure no one runs into the same problem as I did again. Huge shoutout to everyone who helped!
 

MountaineerTom

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Hey all, just got the new core from performance radiator installed today and the heat blows hotter than ever. I will be posting a new thread about everything that happened and what I learned from it to make sure no one runs into the same problem as I did again. Huge shoutout to everyone who helped!
Great news!
 

Davidtj

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Reading this post and the other previous about heat temperatures I have suspected for a while there were issues with some aftermarket cores
Thanks for doing the extra research so others won’t fall in same trap
Here are s another core I have been thinking of purchasing and I think some others on form have used