[JeepinRob]

So in doing some research online ive noticed the Durango has a weird 203° F Thermostat, not an issue. However im noticing if I just start the car and drive around a little my temp doesnt go above 188 but if I sit idle somewhere the temp climbs to 210° then the thermostat opens and the Temp drops. Is my thermostat going bad? Also if I have my temp set to 72° in the cab if im going slow ill have little heat only slight warm.

The only thing I can think of is Thermostat going or I have air in my cooling system.

 

[Don Fox]

JR:
It helps to know year/model/miles on your D. Make sure the coolant level is topped off. You might have a weak t stat. My '04 5.7L takes a good 10 minutes to get warmed up in the 30 degree temps we are presently seeing here in SW Ohio. Once it does though, it will run you out.

Don

 

[JeepinRob]

Oh sorry I have a 2012 SXT 3.6L 112k miles

 

[Don Fox]

That helps. When was the last time the cooling system was serviced? The factory coolant is good for 5 years, or 100k miles. If it's not been changed since new, this is a great opportunity for a new T stat and fresh coolant.

Don

 

[JeepinRob]

Im not the original owner. I just got this Durango about a week ago. I guess ill have to look into getting a new thermostat and coolant flush done.

 

[Don Fox]

Where on the scale does the temp gauge settle once it warms up? The oem coolant was kind of an orange color. While you are at it, the plugs also have a 100k interval. The trans/T case/ and front rear diffs could probably use fresh gear oil as well, unless you can tell that it has been updated.

Don

 

[JeepinRob]

Where on the scale does the temp gauge settle once it warms up? The oem coolant was kind of an orange color. While you are at it, the plugs also have a 100k interval. The trans/T case/ and front rear diffs could probably use fresh gear oil as well, unless you can tell that it has been updated.

Well thats the problem. It doesnt settle anywhere. It ranges from 188f to 210f and currently the coolant that I can see is orange. But I will do a double check tomorrow. I will get new plugs this week. And transmission I noticed when its cold it does some very strange shifting. Almost as if it short shifts from 2nd to 3rd.

I live in PA and its cold as hell here. Wont be doing any of this in the driveway. LOL

 

[Don Fox]

You can handle the plug issue at your leisure. They don't magically expire at 100k. Do you have an analog temp gauge in addition to the digital readout? Once the engine is up around 200, it should not really drop below that unless you're in Alaska, or the Arctic lol.

A drain refill/filter change for the trans with a good grade of ATF+4 would be another thing on your leisurely to do list. Don't forget T case, and front rear differentials as as well.

Don

 

[JeepinRob]

What gear oil for the front and rear diffs. And come on man we live in the damn arctic. PA regularly sees single digits. LOL

 

[Gray Rider]

So in doing some research online ive noticed the Durango has a weird 203° F Thermostat, not an issue. However im noticing if I just start the car and drive around a little my temp doesnt go above 188 but if I sit idle somewhere the temp climbs to 210° then the thermostat opens and the Temp drops. Is my thermostat going bad? Also if I have my temp set to 72° in the cab if im going slow ill have little heat only slight warm.

The only thing I can think of is Thermostat going or I have air in my cooling system.

I have the same scenario and same thoughts as you do.
Even on 25° mornings idling at work the coolant gauge will climb between 1/4 line and 1/2 line mark. I don't have a numerical coolant gauge so my oil temps climb upwards of 203-206, 210 and I don't see or hear the rad fan kicking in.

Now while driving highway speeds, the coolant gauge stays at the 1/4 mark and the trans and oil temps are 186 or below. It does take a little while to warm up but not excessive to be concerned. The only time I smell coolant is when the temps are past 200.
This is on a 2018 GT AWD 3.6 V6. Seems common to me.

 

[Don Fox]

A good brand name synthetic like Mobil 1, Amsoil, Royal Purple, etc in the 75/90 weight will be fine for both front and rear. If you plan to tow frequently, hot and heavy, you might consider 75/140 for the rear.

Don

 

[JeepinRob]

A good brand name synthetic like Mobil 1, Amsoil, Royal Purple, etc in the 75/90 weight will be fine for both front and rear. If you plan to tow frequently, hot and heavy, you might consider 75/140 for the rear.

Don

I dont tow heavy often but its always good to be prepared. I can do the diff fluid change myself.
But I will start looking around for plugs and diff oil. And then Im gonna bring the Durango to Dodge there are 2 opens recalls Im gonna have them fix those and see what they would charge to do the trans service.

 

[JeepinRob]

Well it seems as though my thermostat is bad. But really cant be 100% positive. The last few days its been normal up and down temps. But this morning in the way to work I noticed my temps were starting to creep up higher than normal (highest ive seen in the past week of ownership was 210 which dropped back under 195), but this morning I saw temps of 222 and at one time 230. On the way home this afternoon I hit 237F and pulled over. Overflow tank was empty. And I could hear coolant in the heating system move around on start up.

So I would guess thermostat but why would I get heat at 195 but ice cold air when the temp is up to 225 or so. Its parked now and ill take my Jeep to work tomorrow.

 

[Don Fox]

What were the ambient temps when you saw these readings? It sounds like you have some air in the system. The 3.6 cooling system is not an easy one to remove the air from. If the T stat is oem, I would get a new oem one, and then top it off/burp it as best you can until you have no more air in it.

Don

 

[JeepinRob]

What were the ambient temps when you saw these readings? It sounds like you have some air in the system. The 3.6 cooling system is not an easy one to remove the air from. If the T stat is oem, I would get a new oem one, and then top it off/burp it as best you can until you have no more air in it.

Don

Here in Northeast PA it was 35F. I will try to burp the system Friday or Saturday after I put a new Thermostat in. Its a 30 minute job. So with the air in the system isnt there a bleeder valve on the thermostat housing

 

[DuRonbo]

If the coolant recovery tank was empty....it seems like you have a leak.

Like Don says.....most likely air in the cooling system causing funky readings. And the 3.6L is a giant PITA to purge. I have a friend that's a reputable mechanic that did an engine swap on his old Ram work truck and he couldn't purge the air with conventional methods until he bought a tool set like this:

https://www.amazon.com/JIFETOR-Radiator-Automotive-Pneumatic-Antifreeze/dp/B08BG13XHM/ref=sr_1_1_sspa?dchild=1&keywords=dodge+3.6L+coolant+purge+tool&qid=1610584829&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyQ1VRNzVXSzFZM1dJJmVuY3J5cHRlZElkPUEwMTA1Nzg4MU01N0JJU1dXUUQ5RCZlbmNyeXB0ZWRBZElkPUEwMzQxNTcyMUNYVjVIUUxXUDQwUSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

https://www.amazon.com/M31-Cooling-Internal-Passages-Radiator/dp/B08DFCZM56/ref=sr_1_8?dchild=1&keywords=dodge+3.6L+coolant+purge+tool&qid=1610584829&sr=8-8

You need to get the correct coolant and fill and determine if there's a leak along with the air purge.

 

[Don Fox]

For the 3.6, I cannot say. The 5.7 has one on the front of the water pump. I would Google around, and look for a video to help you there.

Don

 

[DuRonbo]

Here's the procedure from the Factory Service Manual to bleed air from the system on the 3.6L:

 

[JeepinRob]

Here's the procedure from the Factory Service Manual to bleed air from the system on the 3.6L:

Well I have it saved but I dont have an air compressor. So I will need to see if I can borrow my buddies. Seems like a piss poor design that you need a vacuum tool to properly bleed the system.

 

[DuRonbo]

Probably can get a "Pancake" air compressor from Harbor Freight fairly cheap that will do the job.

I'm sure other Auto manufacturers have "Poor" designs for some of their engines too. It's not just Chrysler/Dodge/Jeep.

It's not like the "tools" cost thousands of dollars where only dealers can afford to have them. Did you check all the fluids including the coolant before you bought the vehicle? If not...it's on you. And it's an 8 year old vehicle bought used. Good luck with whatever path you take.