I would swap the factory fan shroud and clutch fan back in and see if the problem goes away, if it does you know its an airflow issue and not something else. I have seen people spend hundreds or even thousands of dollars on aftermarket radiators, high flow water pumps and e fan setups just to have overheating issues later, swapping back to a correctly working factory setup often fixes the problem.

 

What is the cfm rating of the fan you bought? They didn't list it in the link you posted. And as the pics tell the shroud is not covering all of the radiator. You need to make the shroud larger to cover all of the radiator surface. You can try putting the stock shroud over the e fan if you have clearance. The air flowing out may cause some to pass through where the e fan shroud doesn't cover.

 

Radiator looks to be the problem. 1.25 inch is the small one. Summit makes some high performance aluminum radiators for the 5.9L at a similar price to the parts store units. Make sure to get a crossflow unit, not a downflow, as a crossflow is more efficient at rejecting heat. It would be worthwhile to go ahead and check for a head gasket leak, just to make sure you don't have 2 problems.

 

https://www.summitracing.com/parts/csf-3516

This 1-5/8 core CSF is what I had in my truck pre-race conversion.

 

Wish I woulda known about these. Lol I paid more for a thinner one.

I may have discovered more of the problem as well. I took it wheeling again, albeit a much cooler day, in the 80s due to overcast from tropical storm. When moving slow or idling the fan came on like it was supposed to around 185-190ish, when going around 10-20mph, the fan wouldn't come on until around 210-215 or if I stopped. The fan relay came with 2 temp sensors, a fitment for the cooling line itself or the radiator pokey. I choose to poke the radiator (near the inlet). I'm wondering if that "poker" (as I can't think of the correct word right now) is picking up some air flow and cooling it down preventing it from reading the proper temps. I also discovered that on "Max AC" setting the fan intermittently shuts off randomly for several seconds before coming back on, on regular AC it seems to run continuously (although I need to run some more tests to ensure that's an accurate statement). I stabbed the radiator from the engine side, it is not all the way through the rad however the end of the temp probe is showing from the front, sitting almost flush with the face of the rad.

I'm going to take some of these other suggestions as well to ensure there aren't other issues (gasket test ect). I'm nervous about installing the coolant line temp sensor as I've never done that b4, however I'm sure YouTube could show me how. In the meantime I'm going to message FF dynamics and see if this is normal, with a picture of my install (I'll add one here later as well) and see if maybe a faulty temp sensor or relay or just a bad install.

In the 80° ambient temps and overcast, I did some pretty aggressive wheeling with the regular AC on low and it didn't didn't to creep past 200° until I would come off a high rev burnout and then head down a trail at 10-20mph which when I rolled the window down after stopping at 210-215° noticed the fan just then kicking on. Weird.

Also, I just wanted to say, to everyone responding on here, THANK YOU. I got faster responses than I ever expected and great info, glad to have found this forum.

I'll update on what FF says and with pic of my install on the temp sensor to see if I botched that.

 

The word you're looking for is "temperature probe." If you're thinking airflow is an issue, when you get a final resting spot for the probe you can cover the fins in front of the probe with silicone to block airflow over the probe. You don't need a lot, just enough to block the fin it's plugged into and maybe the ones on either side.

On the AC, it should only be coming on when the compressor is on. Ironically enough, when set to max AC the compressor may run less, because it should be running the air conditioner on recirc instead of fresh air so it's mainly cooling pre-cooled air rather than trying to cool down outside air that's being pulled in.

On the radiator, even though the one you have is a new one I'd get the larger one if this is going to tow regularly. If you don't have one you'll also want an aux transmission fluid cooler, not just the one built into the radiator. Plumb it so it goes through the aux cooler first, then the rad cooler, because the rad cooler will heat it back up if the aux cooler cools it too much. Transmissions don't like cold fluid any more than they like hot fluid, they like it to be "just right." Plumbing it through the rad cooler last will make sure it sees a very consistent inlet temp no matter how hot or cold it gets outside.

 

Ya, Temp probe is what I was looking for.
Good idea on the silicone.
May need to try that, when I was wheeling on max AC it got hot, on normal it didn't. I'm wondering if its the 3 things combined that brought about the overheating that day, max ac letting fan cut off (due to compressor), the high heat of that day at 97° or so and the probe getting some air. If it's the probe, isolating and fixing that (gonna try that silicone) may correct the issue.

 

On the probe vs air conditioner, one does not override the other. If the probe calls for the fan to turn on, the fan will turn on regardless of what the AC wants. If the AC calls for the fan to turn on, the fan will turn on regardless of what the probe wants.

I'd also make sure the probe goes in exactly like the controller's directions say, at the radiator inlet or outlet. When putting the silicone in, you also want to make sure to not get it on the probe itself. It won't affect it electrically but may insulate it from the radiator so it doesn't get an accurate temperature reading. All you need here is a wind block.

 

I've got a CSF 3516 with 1.63" row, but this is for the 4.7L. Not sure if it would fit the 5.9, or if it can be made to work.

https://dodgeforum.com/forum/2nd-gen...-radiator.html

 

Right. The 2 differences with my 2 wheeling trips, one temps hitting 230ish and one not going over 215 while wheeling harder was the air setting. Which leads me to believe that being on Max AC and the ambient temps outdoors allowed the issue to show more. Could still be the probe (hopefully) in both situations.
After I was cruising a trail, got right up to 210-215 (with air off) so I rolled down window and stopped truck then heard fan kick on. Fan is set to start up at 185-190 (180 tstat), it should've already been on. Then I continued wheeling, pretty hard, with the air on low (normal ac to get fan running) and temps never really climbed past 200. Actually went down to 175-180 for alot of it.
Whereas the first trip, max ax entire time, some light wheeling with mostly trail riding got to 235ish. If that probe was getting air while cruising around st 15-20mph on the trails that could've been the culprit. Didn't check at the time cause I figured the fan was working. Maybe I should install a little dash led light to tell me when the fan is on. Lol would allow me to diagnose easier at least and rule out fan/probe or confirm it.