Have you had the cooling system flushed? If not I’d try that first, could also be the water pump going out. Either one of those would cause these issues, with regards to the way it heats at higher rpm’s. Wouldn’t hurt to put an aftermarket temp gauge on it even if it were temporary so you could see the actual temperature in degrees.

 

No I have never flushed it lol. Most likely needs to be. The 1st time I had this issue was actually December 2023. Was like 25°F outside at like 2am. The engine wasn't even hot. Every other time it happens it's 80°F or more and the engine is a furnace. I am starting to think maybe I didn't bleed it correctly / long enough.

 

I'll 2nd getting another temp gauge involved to verify that the readings you are seeing are correct. While your coolant, if it's the oem fill, is due to be changed at 10 years, I doubt it is the source of your overheating.

I'd get an oem 203 degree T stat back in there, and bleed the system properly, and see where that takes you.
You state that you feel that the radiator fan is operating correctly. Please explain how you have concluded that?

Don

 

A 2nd temp gauge sounds like a good idea. The fan still works on low and high settings and actually lowers the temp when it goes into high. Unless the Tstat goes out again. The fan tries to lower the temps. It basically bounces up and down when the high fan activates but then shoots straight to H. I replaced my Tstat last night and it solved the overheating issue. But never solves the RPM issue. The Tstat was actually burned when I took it out. Never seen that before

 

Are you bleeding the air out of the system after replacing any of the engine cooling system parts? For example, some cars have the air bleeder valve on the thermostat housing as shown in the picture below. There is also a burping technique used to get air out of the system (search on YouTube). There is also a process used to fill the coolant system via a vacuum process which helps remove the air from the system.

Also, is the thermostat installed in the proper direction? See the picture below.

 

We know that 180 deg thermostats don't work well in the DD and thermostats from the parts stores are probably not going to last long as you keep finding. You need to follow the proper process of bleeding air out by lifting the front of the car up on ramps to help get the air out. If you haven't done that then that critical step is missing. It should have been done every time you opened the cooling system and worked on it. This method requires the cap to come off, a bleeding funnel with coolant in it to be inserted and the engine to be started with both heaters on full blast hot. Then when the thermostat opens and the heaters blow hot you will periodically rev the motor to 1200-1500 rpm and back down, squeeze the upper hose and wait for the air to work its way out of the system. It will bubble up in the funnel as you watch. This will take a about 45 mins on a 5.7 motor.

 

Yeah the 180°F Tstats are not good. Especially Mishimoto. Whatever you do don't buy those. I had better results with the cheap Rock Auto 180. The OEM 203's seem to last alot longer. That is what is currently in it. I think trying to bleed the air the way you described will be the next step to solving this. The Tstat I took out last night was burnt / had burnt coolant on it. Never seen that before.

 

Could be coolant leak on reservoir or leaking in coolant housing

 

The only leak I have is the heater core hose elbow. Only leaks when the heater is on.

 

I will second the motion to check and replace the water pump. The cause here isn't the thermostat. That's a symptom.

Second, the correct coolant is required. You need the purple Mopar OAT. Not Dexcool. Too often, I've seen where deathcool was put into a modern Chrysler product, and you will have the devil of a time flushing your system out afterwards.

Third, do you have all of the radiator seals back in place, after you replaced the radiator? That will affect cooling. A bad coolant temp sensor will also muck things up.

Last, you don't want to be seeing temps much higher than 230° in a hemi. They don't like to run too hot. I'd be curious to know just how hot you've actually had it, but your description leads me to believe the engine's top end is probably misbehaving at higher RPMs. A leak-down test may soon be a necessity.

 

Yes all the radiator seals are there. I already replaced the coolant temp sensor. Did that December 2023 when tstat gave out in 20°F weather at around 2am. Replaced it bc the engine was ice cold. Only to find out it didn't change anything until I put a Tstat in it. I also use Peak North American 50/50 "Orange". I bought the car with this and been using it ever since. Also it completely overheated 3 times now. First being the radiator. I never got a warning on my dash for it. I just happened to look at my temp and saw it at 3/4. By the time I parked it smoke poured out the engine bay. That was by far the worst so far. Since I always watch the temps. Last night was actually the first time my dash warned me about temps. So I caught it early enough to turn it off. Plus I was just sitting in the parking lot when it happened. Which is also a first. Usually only when the temps go up and then never come down due to the RPM issue.

 

You're using the wrong coolant. You have to use OAT coolant only. That is the purple one. Your coolant should NOT be orange. This could be the source of the entire problem. You might have clogged the block up.

 

Well my Mom has had her 2014 Durango since 2014. Used the exact same coolant as me and has zero problems. She also bought her Durango with that coolant in it same as I did with mine. You could be right though. I will try flushing the system and adding the purple Mopar coolant. Plus this time the coolant was burnt on the Tstat.

 

Ziggy:
Depending on what month your '14 was built, it may have come with the older HOAT 5/100 orange coolant. Keep in mind that the updated purple OAT coolant will migrate towards a dirty pink color as it ages.

I've been quite surprised lately by a couple of experiences with GM vehicles where the incorrect oil filter or a fluid quantity was listed in the owner's manual.

Yor comment re "burnt" coolant on the T stat is troubling. I've never see such a thing in 40+ years of auto/vehicle involvement.

BTW:
The leak at the heater core should be fixed. It can allow air to be drawn back in as the cooling system is returning to ambient temps for the evening/night. This may also keep the system from maintaining proper pressurization which can also cause overheating.

Don

 

Changeover to OAT was 2013 MY. My '13 has a July '12 build date, but came with the OAT.

 

NT:
That's good know.
My '14 Charger built 09/13 also has the purple OAT. We have had folks here though with vehicles in the changeover period with both. I have to believe they won't throw away new coolant, but will use up what the have then make the switch. It makes good business sense anyway.

Don

 

I bought mine used with 132,000 miles in 2021. When I did it already had the Orange coolant. My Parents have 2 2014's. One is a early 2014 and the other we have no idea. Both have the Orange coolant also so I thought it was fine. Makes me wonder how and why my 2015 got the Orange stuff to begin with.

 

I think you smoked it. At the very least, you might've lost the head gasket on at least one side. The 230° that I mentioned was in a 2015 tech bulletin that was printed out for me at the dealer.

Tear it apart. Use Mopar parts for everything but the water pump. I think the USMW pumps have the larger bearing. Chrysler recommends a triple flush to get the nasty Deathcool out of the system, then use the correct OAT coolant.

Sorry, but that's the harsh reality you're looking at.

 

Was the cooling system burped of air pockets

 

Could it be a stuck heater control valve?

 

How are you determining that the thermostats are actually bad? Can you post a picture of this burned thermostat?

 

Alright sorry for the late update. Recently had alot happen in my personal life. Anyways I figured it out. I replaced the Tstat with a oem 203°F one. My Durango started doing the opposite. It would overheat on idle and drop as soon as I took off. Which was odd. So I thought it was the water pump. Before I decided to change it out I tried to see if there was any more air somehow in the system. I previously tried to raise the front end up and burp it. No air came out. I So I opened the radiator and squeezed the upper hose. Air bubbles rose out. I spent 40mins squeezing the upper hose, adding coolant till it stops bubbling, turning it on and reving to 4k for 5secs, turning it off and repeating. After spending almost and hour and adding 1 1/2 jugs of antifreeze straight to the radiator I couldn't get anymore air out of it. I closed everything up and took it for a drive. Now the overheating has been fixed. Ik not your conventional way of burping the system but like I said raising the front end and letting it run for 30mins did not work for me.

 

Ziggy:
Congrats on getting it fixed. You are correct that elevating the front and just idling it with the system open won't work.
Squeezing (carefully) the upper/lower hoses helps a lot. You don't have to rev it to 4k, but 2-2.5 is helpful. This is not a quick process, by any stretch as you have learned.

What you did is exactly what was needed. If you think that was challenge, the 3.6L is worse!!!!!

Don

 

Turn it on and off during the purging was not necessary but glad you got it working.