Hey everyone, running in circles trying to fix this overheat problem.
2016 f150 5.0 230k miles.
This was a company truck I drove since new, for the company I work for. When it hit 200k, it was due for sale and they sold it to me at a great price. The truck started running pretty hot, but not "overheating" and tripping the safety. It was getting very hot at freeway, but not idle. I replaced the water pump, belts, idler/tensioner pulleys, and thermostat(motorad). They were original, so it seemed to be a good preventative.
It ran fairly normal for 9 months, then started actually overheating. Same as before, overheating at freeway cruise, not at idle. Still getting plenty of heat from heater. Replaced the radiator, it was partially clogged. Replaced the thermostat again, it's still overheating.
Any ideas? Bad Motorad Thermostat? Bad water pump?

 

If the truck was not running hot prior to your work, I'd suggest replacing the thermostat with a Motorcraft unit. 99.82% of these newer trucks that toss the OEM thermostat claim heating issues until the Motorcraft t-stat is installed. The Motorcraft design is different than what you'll buy at a parts store.

 

Thank you, I've read a lot about issues with the aftermarket stats.
I've been working on this all day.
​​​​​​I think it's the CHT. The temp reading started getting erratic. Just got home, used my clamp temp probe and infrared. Highest temp I could find was 160. Radiator outlet was 85! My truck is not overheating, but the computer thinks it is. Of course I found this after posting.

 

Well, I thought the temp hunting was a bad CHT. Replaced it today and nope, same thing. I'm back to either the thermostat or water pump.
The heater works great. The engine temp shows 220-230, with occasional drops to 205. The radiator inlet is 165, the outlet is 65. The thermostat housing is cold to the touch, behind the thermostat is very hot. It doesn't seem to be recirculating water through the thermostat. It's brand new, the one before it was also new. Could aftermarket stats really be that bad? 3 thermostats in a year???

 

There have been tons of posts detailing bad aftermarket thermostats and others showing big design differences. Put a motorcraft thermostat in it

 

I would give a 3rd vote for an OEM thermostat.

While not entirely related, similar overheating issues seemed to take place after cam phaser jobs and I think some users fixed it with a new thermostat.

Your temp reading data seems like a few good clues.

 

Had my 2016 5.0 in for a water pump replacement under warranty. While they were in there, I had them replace the coolant tee, o-rings, thermostat at the same time. Driving home I was at 235-240.

Replaced the cylinder head temp sensor. Same problem. Stopped back at the dealership the other day, and even though my receipt had a Motorcraft part number, they used a non-OEM thermostat because they couldn't get the Motorcraft in time... Ok... So, I am now putting in a Motorcraft unit expecting that to fix the problem. If I run the RPM's up to 3k-3.5k, it drops immediately down to 205-ish. I had been locking it in 3rd gear to run 60mph at about 3k/208-210 degrees. I am assuming that the non-OEM does not open correctly and needs the extra flow at higher RPM's to cool down. Even the service guy at the 2nd dealership I stopped at said to change the thermostat to the Motorcraft one.

For the 5.0L in my 2016:
BR3Z-8575-F Thermostat
BR3Z-8255-A Gasket/O-ring

 

I got an aftermarket heavy duty radiator, and a 180 thermostat. Is it possible the radiator is rejecting too much heat, keeping the thermostat closed?

 

That sounds exactly like what I'm experiencing. I have to drop it to 3rd or 4th, get the rpms up, to get the temps to drop. That's why I was thinking it may be water pump.

 

No reason for an aftermarket or different temp thermostat.
Try an OEM part.

And if you had infinite cooling in the radiator the thermostat would still regulate as needed.
Sounds like it is not working correctly.