2015 EL 4x4 3.73s with max tow package 172,000 miles. At 116,000 miles it got a water pump, Tstat and coolant flush. Empty all day around town in the AZ heat up to 115° outside the truck will run 190°-205° coolant temp (on Scangauge) and trans temp around the same. When towing my 5100# tritoon 65mph on the freeway in 5th (6th locked out) it would normally run 210°-220° with outside temps 90s to low 100s. Recently towing the boat I started seeing temps into the 230s on slight inclines then down to 210-215 on the downhills and A/C temps would get a little warmer in stop and go traffic then cool off at highway speeds. I could hear the cooling fans running on high but it fooled me until I checked the fans at night with a flashlight and found only the driver side fan would run. So swapped out the fans (both new fans is a complete single unit). They are both definitely running now. And immediately noticed an improvement in A/C temps at slower speeds and thought my cooling issue was gone then we made our first lake trip since the new fans and I saw a high of 233° pulling a decent hill in 4th. It didn't seem to care whether it was pulling 4th or 5th gear at 65mph the coolant temps stayed high.

Is my Tstat not opening all the way? Empty temps are normal though....
Radiator looks normal for 172,000 miles but possibly just caked with too many bugs?
Only 56,000 on new cooling system except radiator.
I'm thinking of doing a radiator, Tstat and coolant flush? Not too expensive........

Is that what you would do?

 

Side note, the temp gauge on the dash doesn't even start to move until my Scangauge shows 230°. Thanks Ford for the fake gauges that are just dummy lights with needles.

 

Okay so replaced just the thermostat with a Motorcraft 188° (exactly what was in it) and yesterday was the first chance I had to tow with it again and it did the exact same but maybe just a few degrees cooler but it was a different day with definitely more humidity so who knows how much that could affect it.

The max I saw was 234° running 65 mph in 5th gear and if I backed down to 60 mph in fourth gear temp came down to around 222°.

But reading more about this people mention a temperature sensor on the back side of the passenger side head that gives these erroneous readings even when it's not actually that hot but it sure is tracking like an overheating engine would. Problem now is I can't see and can barely touch this temperature sensor with two fingers so how the hell am I supposed to change it and then is it going to fix my problem. I don't want to just keep throwing parts at it.

So now on my to do list is a new radiator and or this temp sensor I still would only want to do one at a time to verify individual results.