5.7 overheating when towing in mountains

[Albab930]

I apologize in advance for the long post but I really need some help and want to provide the necessary info.
I have a 2021 Warlock with 5.7 Hemi and towing package. It has 38,000 miles on it and I’m the 2nd owner. I bought the truck specifically to tow a small travel trailer of less than 4000 lbs. it is a single axle trailer and is 20 ft long and I have verified the loaded weight on a Cat scale. I use a weight distribution hitch and all is set up correctly by a competent shop.
Trailer pulls fine and truck runs great on relatively level or short grades but in Colorado, things are not flat. The problem is on long and steeper grades the engine overheats. First experience was coming east up I-70 to the Eisenhower/Johnson tunnels. Ambient temp was 65 degrees and the engine hot warning alert happened less than 1/2 mile from the summit. I immediately slowed to about 40 mph and entered the tunnel and down grade where I let off the gas and began coasting down hill. Warnings went off and temps cooled immediately. I had been surprised by the warning and didn’t check the diagnostic screens for actual temperatures.
I took the truck to a reputable shop. They looked things over and determined the fan clutch was bad and also recommended a new water pump, thermostat and radiator cap. They also drained and flushed the cooling system.
Two weeks later, I hook up the trailer and pulled up La Veta pass. Not a terribly steep grade but a very long climb. Water temp held steady but climbed slowly to about 230 over about 10 miles. Engine temp about 240 and tranny at 193. The last couple miles of the pass are steeper and suddenly the water got to 250 and height temp warning alerted. Pulled over and let idle. Temp quickly dropped back to about 225 as air temp was only 60.
I took truck back to the shop and they were able to replicate the heating under load on a Dino. They have performed a myriad of other tests and say the heads, head gaskets and block all test fine.
What can I do next to resolve this overheating issue. I know it isn’t normal and I see others relating similar experiences on various forums but I haven’t seen anyone really give a definitive solution.
I’m all ears. Thanks in advance!

 

[Curmudgeon]

While I am the last person at RamForums to offer advice, least qualified anyway, Can you say what your differential ratio is? Mine is the 3.21, good on gas but not the ratio I would choose for a tow-vehicle. And I've never towed with my 2014 1500.

I'm guessing you have the 8-speed which is ideal, and it seems you have done everything you could to prep for towing that load. I think the more common rear is the 3.92. Might help? I have read that the difference between the 3.92 and the 3.21 is like manually dropping the 8-speed down to 7th gear. If you use the TOW/HAUL mode this will also lock-out 8th gear.

 

[Albab930]

Yes, I have the 3.92 and I do drop the trans to 7th, and even 6th gear when climbing.

 

[Burla]

See @Hemi395 's thermostat thread and run a 180. Looks like they were throwing parts at it and it didn't work, and you say reputable? If that is true they should fix it. Appears that all 4 repairs were unneeded and it is something else perhaps cooling sensor.

 

[Burla]

In general long grades can expect 250 on OIL temps, I don't think coolant should see that or you have issues, so it is also possible it is user error, that would be the exact temp I would put over and idle down, so not terribly out of bounds. This was likely a situational injury or failure, so as long as this isn't happening on regular streets, pat more attention on grade and pull over and idle down if needed. You have done everything short of radiator, mise well do coolant temp sensor Mopar.

 

[Hemi395]

I went through with my 2013 recently. My coolant temp never got that high but my oil temp would hit 250 on flat ground.

I had to do several things to lower the overall temperatures:

First and most effective was a 190 tstat. I used a Calorstat from Rockauto.

Second thing was to adjust the efan to come on way sooner than the factory settings, you will need to tune for this, for my truck the pcm is unlocked due to the age of the truck so that easy for me.

Third was to get a honeycomb grill since they flow more air than the BigHorn grill that came on my truck.

I have essentially the same travel trailer as you do and my temps have been way lower since doing all these mods. I believe you have the active grill shutters as well? For you I think deleting the shutters and going with a 190 or 180 thermostat would help a lot.

 

[Hemi395]

In general long grades can expect 250 on OIL temps, I don't think coolant should see that or you have issues, so it is also possible it is user error, that would be the exact temp I would put over and idle down, so not terribly out of bounds. This was likely a situational injury or failure, so as long as this isn't happening on regular streets, pat more attention on grade and pull over and idle down if needed. You have done everything short of radiator, mise well do coolant temp sensor Mopar.

Agreed, coolant temp should NEVER be that high...

 

[Burla]

clarify, I would pull over and idle when I saw 250f in Oil temps, I would have pulled over way sooner on Coolant temps, I would likely push it as high as 235f if I saw the end in sight on coolant, if not I'm pulling over 230f. I have never seen anything close in my truck, but then again I haven't towing up grades with this truck.

 

[Albab930]

Thanks for the suggestions. I will go back to the shop and have them install a lower temp thermostat. They put in the stock OEM part and it opens around 203. I have seen a number of other comments about running the lower stat and feel that is probably the way to go. If that doesn't do the trick, I'll look into reprograming the fan to come on earlier. I don't have the shutters on the truck so no help there.
To an earlier comment the shop is very reputable. The fan clutch was bad and I agreed to pull the waterpump as there was a small leak showing. When we took it off, the vanes were pretty loose and sloppy on the shaft and the shaft bearing was allowing some slop so it was on it's way out. I have a healthy distrust of repair shops but have used these folks for a while and I trust them.

 

[MTS]

I went through with my 2013 recently. My coolant temp never got that high but my oil temp would hit 250 on flat ground.

I had to do several things to lower the overall temperatures:

First and most effective was a 190 tstat. I used a Calorstat from Rockauto.

Second thing was to adjust the efan to come on way sooner than the factory settings, you will need to tune for this, for my truck the pcm is unlocked due to the age of the truck so that easy for me.

Third was to get a honeycomb grill since they flow more air than the BigHorn grill that came on my truck.

I have essentially the same travel trailer as you do and my temps have been way lower since doing all these mods. I believe you have the active grill shutters as well? For you I think deleting the shutters and going with a 190 or 180 thermostat would help a lot.

I don't think the ECM will like a 190º or 180º thermostat.

 

[Burla]

I wouldnt sleep on coolant temp sensor, if there was any jump in temps, this would be most likely culprit. And if you have grill shutters, those are a large issue here.

 

[Wild one]

Being in Colorado i'd try a 192 thermostat,as it'll still supply good heat for the winter,and won't cause any issues,a 180 "might" turn on a thermostat rational code,but that's a big "might" as i've ran lots of 180's with the stock tune and never had any issues with codes.Or you could do like me and swap between a 180 for the summer,and then stick either a 192 or the stock 203 t-stat back in for the winter. As mentioned by Cory/Hemi395 what grill do you have,as the grill can make a huge differance on airflow
You want the Honeycomb grill,you don't want the slat/Sport type grill.
Pictures of both,the grill you don't want is the 2nd picture

 

[Hemi395]

I don't think the ECM will like a 190º or 180º thermostat.

I know the 160 tstat can cause some issues but many people run 190 and 180 tstats without issue.

 

[Hemi395]

Thanks for the suggestions. I will go back to the shop and have them install a lower temp thermostat. They put in the stock OEM part and it opens around 203. I have seen a number of other comments about running the lower stat and feel that is probably the way to go. If that doesn't do the trick, I'll look into reprograming the fan to come on earlier. I don't have the shutters on the truck so no help there.
To an earlier comment the shop is very reputable. The fan clutch was bad and I agreed to pull the waterpump as there was a small leak showing. When we took it off, the vanes were pretty loose and sloppy on the shaft and the shaft bearing was allowing some slop so it was on it's way out. I have a healthy distrust of repair shops but have used these folks for a while and I trust them.

Did they use an OEM Mopar thermostat or an aftermarket one? I have had one Mopar tstat be bad right out of the packaging so that could be an issue as well.

The OEM thermostat STARTS to open at 203 and will allow coolant temps to get to 212-214 before dropping them back to 204 or so. Way too hot for towing IMO.

 

[Curmudgeon]

Did they use an OEM Mopar thermostat or an aftermarket one? I have had one Mopar tstat be bad right out of the packaging so that could be an issue as well.

The OEM thermostat STARTS to open at 203 and will allow coolant temps to get to 212-214 before dropping them back to 204 or so. Way too hot for towing IMO.

Mine is all stock, and factory, and these are mostly the numbers I see in the summer. Highway cruising generally provides lower temps though.
My 3.21 rear allows for 1500rpm cruising at 70mph in 8th gear.

 

[Albab930]

Well it was an easy job to replace the thermostat with a 180. Leaving tomorrow to tow the trailer about 2500 miles so we’ll give it a good workout. Will be pulling up a couple big grades and will take it easy but watch the screens closely. Will report when we get back in 3 weeks.

 

[RamDiver]

And if you have grill shutters, those are a large issue here.

There's no AGS on my '21 Warlock.

Well it was an easy job to replace the thermostat with a 180. Leaving tomorrow to tow the trailer about 2500 miles so we’ll give it a good workout. Will be pulling up a couple big grades and will take it easy but watch the screens closely. Will report when we get back in 3 weeks.

Most of the clever users don't trust a new thermostat to function out of the box.
Not before performing a stovetop test with hot water and a cooking thermometer.

.

 

[rzr6-4]

and also recommended a new water pump, thermostat and radiator cap.

Did they use lube when they fkd you? At 38k miles, unless those parts test bad there's no reason to be swapping those out as preventive. They are just getting more money out of you.

How fast are you trying to pull up those grades? Wind resistance from those trailers is huge.

Also, what RPMs? 3-4k would be pretty normal, if you are screaming at 5k for miles I would suspect you are working it too hard.

Had to skim quick and didn't see these asked. Sorry if this has been covered.

 

[Burla]

Well it was an easy job to replace the thermostat with a 180. Leaving tomorrow to tow the trailer about 2500 miles so we’ll give it a good workout. Will be pulling up a couple big grades and will take it easy but watch the screens closely. Will report when we get back in 3 weeks.

Just watch coolant temps, you see 230f pull over idle down, have to idle just like a diesel or you can warp heads when you talking about temps as high as you were reporting.

 

[62Blazer]

Verify if your truck has the active grill shutters. If it does I would be looking closely at those to make sure they are opening. Generally if overheating is occurring at highway speeds I look for airflow blockages to the radiator (i.e. like the radiator with clogged with mud/dirt....and the AGS could cause the same issue). Generally don't suspect cooling fans at highway speeds. That is because you are getting a lot of airflow through the radiator simply running at highway speeds, and the fans are mainly to push air through the radiator when stopped or lower speeds.
Putting a lower temp thermostat is not going to fix the problem at all. A 203 F thermostat flows the exact same amount of coolant when open as the 160 F thermostat. It doesn't change the cooling capability of the system, it just opens sooner. If the cooling system allows the engine to get hot with a 203 F thermostat, how in the world is it going to maintain a lower temp? If the engine is getting up to 250 F with a 203 F thermostat........it's still going to get up to 250 F with a lower temp thermostat. Again, there is zero difference in the capability of the cooling system if you have a fully open 203 F thermostat as compared to a fully open 160 F thermostat.