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Discussion Starter #1
My wife's Durango's heat has been blowing like warm, just a hair above room temp. It's winter in Wisconsin and with four small kids, it's not great. Back in September I had replaced the thermostat thinking it would solve the problem, but it didn't help. Heat still blowing lukewarm. I noticed the passenger side vents were not responding at all to temperature changes, and after some research, decided to remove the glove box to inspect the blend door actuator and gear. Sure enough, the gear was broken. I replaced the gear and the passenger side responded to temp changes again. Unfortunately, the heat still doesn't get hot. Just lukewarm.

The next day a light came on the dash - red lightning bolt between two backwards parenthesis, but went away later on. Her check engine light also came on with the following codes:
P2181
P0128

since the thermostat had a lifetime warranty, I received a new one for free and installed it tonight. Still no improvement, at least at first. I let the truck idle in the garage and topped off coolant, and squeezed the radiator hose repeatedly. Slowly the coolant temp sensor rose to normal operating temp (195-200ish), though it took like 20 minutes. I hopped it and drove around for a few minutes. As I drove around, the coolant temperature dropped steadily all the way back down to 145-150. I went back home and let it sit and idle again. The coolant temperature once again slowly rose to operating temp. I'm at a loss as to why the coolant temperature drops when driving, and rises while idling. I did this idle up to temp, then drive around thing 3-4 times. The heat in the cabin is blowing way hotter now, but does start to slowly cool off as I drive around.

My only guesses at this point are 1. Still some air in coolant system or 2. The coolant temperature sensor is bad.

Does anyone have any ideas? And please don't say thermostat. This is the 2nd brand new thermostat I installed. Thanks for any help you can provide!
 

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Sounds like air pocket to me would try to add more coolant. Make sure you have heat turned full blast while adding coolant and let it get up to temp. That way thermostat is open and heater core is taking as much coolant as possible. Should feel heat get good and hot, but it may take 20-30 mins of idle to get up to temp.
 

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Discussion Starter #4
It's a 3.6l v6 engine and the thermostat was a direct replacement from 1aAuto that was an exact fit according to the website. I didn't test it, but keep in mind I have installed two of them now. The chances that both were bad is pretty darn low I'd think.

I added coolant until full and let it idle for 20 minutes or so. The heat did in fact get hot, and the coolant temp did slowly rise from about 135 all the way up to about 200 degrees. Then I took it out on the road. As soon as I drove around, the coolant temperature would steadily and pretty quickly drop back down to 140ish. I'd say this happened within maybe 5-10 minutes of driving. I did this same cycle a handful of times with the same results.

Right after replacing the thermostat and refilling coolant, the radiator hose was warm and easy to squeeze. After a couple hours of attempted burping (squeezing hoses, idling up to temp, driving around), the hoses became more and more hot and more difficult to squeeze. Before I called it quits for the night it felt full and very hot to the touch. Heat was blowing nice and hot in the cabin. It's just that damn coolant temperature gauge ...still rising to temp slowly at idle and then dropping below operating temp while driving.
 

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Discussion Starter #5
Oh and also in case you haven't picked up on it, I'm not very good at these things at all. When I removed the old thermostat I caught the coolant in a clean bucket. I poured that coolant back in when I was done, but wasn't thinking and poured it into the resovoir, which was at the full line to begin with. So the resovoir had about 4 inches of coolant above full line. By the time I idled and drove around a bunch of times and decided to give up for the night, the coolant in the resovoir was only about an inch above the full line. So I think it's slowly cycling through and hopefully any air pockets are working their way out. Anyways, I just woke up and will fire it up this morning and see if it gets up to temp, stays there, etc. and see where coolant levels are at.
 

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Soules:
You do have unpurged air in your cooling system. From what I have read, the design of the system for the 3.6 makes air removal problematic. It helps to elevate the front of the D just a bit. Have the coolant refill cap off. With the heater(s) on high, let it warm up. When the T stat has opened, run the rpms up to 1.5-2k several times while you observe coolant level, and top it off as the level drops. At some point, the level will settle, heat should be copius, and you are good.

Don
 

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Getting the coolant truly topped off is trickier then it should be. I do not have the v6, but when I recently messed with it I topped off coolant, started engine with heat full blast and let it warm up. Had radiator cap open with funnel in it, and had funnel filled about half way up. When thermostat opened lot of bubbling and coolant in funnel was pulled in. Then kept putting more in till just would not take anymore. Cap back on and filled overflow to full line as well. Right wrong I don't know, but seems to have worked.
 

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Discussion Starter #8
I appreciate everyone's help so far. The coolant level in the reservoir was just above the full line this morning. I opened the radiator cap and the coolant was right up to the neck, very full. I started the Durango and let it idle for about 20 minutes in the garage. I checked the coolant temperature gauge and it was only up to about 165. I had to leave for work, so I shut off the Durango and left.

Unfortunately, my neighborhood is very flat so there really isn't anywhere I can park it at an incline to try to burp the air out. I might have to jack the front up a bit in the garage. I'm also considering flushing the heater core. Does that seem like a good idea? I just can't help but feel like there's something else going on. Even if the heater core was clogged up, wouldn't that just mean that hot coolant wouldn't flow through it and my heat would blow cool air? The fact that my coolant temperature gauge reads cold and takes forever to reach operating temp, then falls back down to cold when I drive makes me feel like there's a separate issue.
 

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Discussion Starter #9
Should I open the bleed valve on the thermostat? I tried it once but coolant shot out like a fountain when I started the engine so I tightened it back up and have been trying to burp the air by leaving the radiator cap off and squeezing the hoses.
 

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Yes:
You will want to have the bleed screw open during this process, at least until you have solid coolant emitting from it, and no more air. What year is the Durango, and how many miles on it?

Don
 

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Discussion Starter #11
It is a 2012 3.6 crew and I am not sure exactly how many miles - it's my wife's Durango. I mentioned in the original post above that I pulled two codes from it:
P2181 and P0128. Some google searching tells me the thermostat is bad (which is why I replaced it - twice now) and the coolant temperature sensor. I actually bought a new coolant temperature sensor, but for the life of me, I couldn't find where the dang thing is to replace it. I scoured the internet for two days trying to figure it out, but ultimately found nothing. Just a handful of other Durango owners with the same engine wondering the same thing, but no answers. I think it might be underneath the upper intake manifold where you can't see it. But I wanted to start with the thermostat first to see if the problem was solved before tearing the upper intake manifold out.
 

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Discussion Starter #12
My wife just reported that she drove around town for a bit running some errands this morning and she said the temperature fluctuated between 160-175ish, but when she let it sit and idle it climbed higher, closer to 190. How much fluctuation should there be? Shouldn't it pretty much climb to operating temp within a few minutes of starting and then maintain that?

By the way - does ANYONE know the location of the coolant temperature sensor on a 2012 Dodge Durango Crew with 3.6l V6 engine?
 

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Discussion Starter #13
I am going to do a heater core flush this weekend. Where exactly are the two heater core hoses? Somewhere up near the firewall, but driver side, passenger side, etc.? Any tips you all can share with me would be appreciated. Thank you!
 

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Discussion Starter #14
I worked on the Durango for several hours today. First, I flushed the heater core. Ran water through it, then ran some CLR through and let it sit for 15 minutes or so. Then ran more water through to clean it out. It was actually pretty clean, so I am not sure how much that helped, but I suppose it couldn't have hurt. Then I started my quest to find the elusive coolant temperature sensor. I had read at one point in the comment of a YouTube video that it was located in a "water jacket" toward the back side of the engine block on the driver's side and that you had to remove the upper intake manifold to access it. So that's what I did. I removed the upper intake manifold, which was a bit tricky. For anyone looking to do this on their Durango there are some really helpful YouTube videos that show the location of all the bolts and studs and some tricks on how to remove it.

After searching all around with a flashlight, we finally located the sensor. If's on the side of the engine block maybe about 8 inches to the left of where the steering column enters the firewall. Look for a plug that goes into what looks like a white-ish colored plastic circle. It has a red clip you have to unclip and then the wire pulls out. I was able to maneuver the white "water jacket" up the wire a bit so I could see the sensor and used a socket to remove it. I have to say, this process sucked. It's a very tight space because of the metal AC hoses that run through there. Very hard to get a socket on the old sensor and also very hard to thread the new one in without dropping it or your tools. In fact, I ended up tying a string to the tool I was using and then tying the other end of the string to the hood latch. Got real tired of dropping it and wasting time feeling around for it. I actually snapped a couple pics of the sensor location because I know there are people out there who will scour the internet like I did trying to find that info and come up short. Here you go!

This is where it's located.

108176


Below pic shows where the sensor was after I removed it.

108177


Anyways, I was able to get the old sensor out and installed the new one. Then we put it all back together, filled with coolant, let it burp until it wouldn't burp anymore, and then test drove it. The good news is, the temperature no longer drops when we drive it. It remains consistent within a few degrees. The bad news is, it only gets up to 170 and then stays there. After all of this, I'm convinced that the thermostat I got from 1aAuto is rated at 170 degrees. That would explain why the brand new replacement they sent is also maxing out at 170 degrees. I purchased a new thermostat from a local auto parts store and made sure to confirm it is the OEM replacement, which is rated at 203 degrees. It did not come with the housing, so I will have to see if I can remove the thermostat we just installed and use that housing for this new one.

I believe we had a couple different issues going on, and that they are all solved, however our thermostat is rated for 170 degrees, which is why our coolant temp gauge stops there, and also would explain why our fuel economy has been awful (16-17 mpg). Hopefully this helps someone out at some point.
 

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Soules:
Glad to hear you have made good progress, and kudos for the associated pics. It's great when folks can document their process for the next time someone has to go down the same road.

Don
 

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Discussion Starter #16
Thanks Don. I was so frustrated that nobody knew where it was located, so when I found it I felt a duty to snap some pics. :)

Now I just need to figure out how to put the new thermostat into the housing of the other one. I hope that's possible...

Oh and I forgot to mention. I found some kind of bleeder hose to the right of the upper intake manifold. It had a greenish blue cap on the end and it had broken clean off. My father in laws Jeep has the same engine, so I found the same hose in his and followed it back to where the heater core hoses enter the firewall then lost it from there. Does anyone know what this is? Mine looked like it had burned/ripped in half.
 

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Discussion Starter #18
I can't but help think the Heater core is clogged ro something.
That's why we flushed the heater core. First we blew it out with an air compressor, then we ran clean water through, then we ran CLR through and let it sit for 15 minutes, then we ran clean water through, then air again, then filled with new coolant. There was very little crud or deposits that came out, so I don't really think that was the issue, though it certainly didn't help. My best guess is that there was air in the coolant system, and it eventually worked itself out. It did burp quite a bit once we topped everything off at the end. Between the heater core flush, thermostat replacement, and coolant temp sensor replacement, we drained quite a bit of the coolant.
 
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