I know this subject has been beat to death, but my issue doesn't seem like everyone else's.
I have a 2003 NF-155, 4x4, Lariat, Automatic, 3.73 rear end, 4R70W tranny, 3in body lift, 35in tires, Edge Evo programmer, all stock otherwise.
My issue is this; when driving normally, to work and back, on any day when its below 85-90 degrees outside, my truck will run at normal operating temperature. I have a 180 degree t-stat in it and my edge programmer never moves above 186. This includes towing or not. A/C on or not. doesn't seem to matter. Once the outside temp creeps above 90, my truck will run around 214 degrees. Under heavy stop and go traffic when its above 100 degrees out it will run closer 220-230 degrees. I have replaced t-stat a few times but they always seem to work fine. i can watch temp go down on programmer when t-stat opens so i know it works. I have flushed radiator a few times but it doesn't seem to change anything. Fan clutch seems ok, only thing left i'm contemplating is a new radiator, hoses and maybe the water pump. Any ideas? Kinda stumped on this one.

 

If the radiator bottom area is plugged, it restricts the flow volume and could put the cooling system at a margin for cooling at some high ambient point.
The pump vanes could be at cause as well.
You need to get to the cause before towing in hot weather.
As well the trans heat load also enters into this.
The normal thermostat runs the cooling system at near 200° +/-.
Normally a lower thermostat is not a good idea because the PCM looks at the cylinder head temp as a means of adjusting timing and fuel injection amounts.
For example if you install a larger capacity radiator with the stock thermostat the only thing that works a bit different is the thermostat opens and closes more often to maintain the average system temperature because it is open a shorter time each time it opens due to the extra cooling out of the radiator it senses before is closes again.
The engine still runs at the same average temperature dispite a larger radiator.
Good luck.

 

big tires, lift kit, hot temps, old radiator... i might consider a new radiator, one slightly larger...

 

214 is not overheating the 220-230 is getting somewhat hot but would still be out of the red. Would be interesting to see how a pair of Efans would handle it.

 

I agree your current radiator has some cores plugged or restricted. If you have the funds I would do a new radiator with twin fans as suggested. At least a radiator. I doubt its the pump but I have been wrong before.

 

fan works in town when stop and go traffic. Should not make any difference at 50-60 MPH on the highway.

 

Well, finally got a chance to get back on here. First off, thanks for all the ideas and input. Much appreciated. So here's what I've done so far: Changed radiator to a two core, new upper and lower hoses, new water pump and new fan clutch. Over $300 later and it changed nothing. WTF!! The only other thing I can think of at this point is the ECT sensor. From what I've read, it sounds like a bitch. Is there any way I can check it without pulling off my intake manifold. I don't see many options left.