Does your thermostat have the little whole near the outer edge to break up potential air bubbles? This is a must, if not than drill in hole and make sure the hole is at 12 o'clock when mounting in truck.

I had some success with using a bottle a water wetter and purple ice, one or the other.

 

Thermostat has the hole at 12 o'clock position..will give the water wetter a try thanks

 

I know it may seem odd for a working truck but a bottle worked in my case.
Disco Mike also has it posted on a sticky as part of the maintenance.
https://landroverforums.com/forum/di...h-miler-42471/

 

This was posted on the forum awhile ago and I brought it up in a post in 2016 as part of my to-do-list. It never got done and while reading thru older post trying to help troubleshoot your over heating issue I found this thread again that I thought would bring me closer to resolving my overheating issue. If I can figure out what size I need I think I would have ordered this years ago. Just a another little tool that stays under the hood along with the fuel pressure gauge installed.

Coolant Sight Glass
https://jagsthatrun.com/products/coo...=7267760832555

 

I forget if you replaced the fan clutch. In either case I stand by this quote. Get a $12 IR thermometer from Amazon and take a look at your radiator for 'cool' spots which suggests uneven flow through.

If the radiator hasn't been maintained for 20+ years, I'd bet it needs some attention.

Temps here in NYC were 95-100 over the past few days and the hottest mine ran (while in motion) with the A/C on was 207. The e-fans just can't keep up with it is that hot so temps move up another 5-10 when standing still. Fan clutch is locked up (easy to hear) but idle speed is not enough.

 

Use a laser temp thing and look for 20 degrees difference between the bottom and top, It’s possible to have a radiator that’s not flowing in the lower half, you can sometimes look down the fill or vent, and look at the ends of the tubes... if there’re covered in white crap you have restricted flow to some level. Pull the radiator and lay it down and fill it full of CLR for 30 mins to an hour and see if it gets better. Every time I’m stuck it turns out to be an inefficient radiator OR a leaking head gasket generating more heat than ANY cooling system can manage.
do you have the correct fan shroud? This is also a major factor.

 

Check and make sure the lower hose isn’t being sucked flat at speed. Olden days there was a spring in some lower hoses to prevent that.

 

Ok, (deep breath)
lower hose is not being sucked flat, feels like a spring is in there,
Viscous clutch has been replaced, no change. thermostat was changed with a 180 degree one, no change, Upper radiator hose had a bit of swelling at the ends so it was replaced, no change.
I have an IR temp sensor and I verified that the temps I am seeing on my OBDII scanner is accurate with what is read at the upper hose /thermostat housing.
I have not checked the temp differential from the top and bottom of the radiator (I will check that)
coolant looks to be new, no oil and no coolant in the oil, and level does not change in last few weeks, exhaust seems clear, no coolant smell or moisture.
fan shroud is the stock unit and looks to be complete comparing it to my '98, fan blades also match (not installed backwards)

The strange part is that it gets much warmer at higher speeds, and runs cooler at city speeds. Exact opposite of what you would expect. E-fans are new, and working correctly. I like the idea of the coolant sight glass!

keep in mind that this is a 'new truck to me' and have no idea what the previous owner has done to it, but I have fixed a number of other issues.
I do appreciate all the suggestions!

outside temps were mild today, low 70's and it only hit 218 a few times driving at 65 mph going up a slight incline, then went back down to 215 until I got onto side streets, 45 mph it was around 207-211. Driving home at night (around midnight) outside temps around 66, it stays around 200-207 on highways, and when I get into town, 30-45 mph it can get as low as 188 at times.

 

Well, fan turning backwards would match your symptoms, any chance belt is misrouted or fan backwards? Reason I ask, I got mine cheap because the belt was misrouted.

 

That I did not check... did some rough temps on radiator, 186 at inlet and 126 at lower rad hose, center of rad at bottom looked to be 157 (hard to get an accurate temp, but there is definitely some cooling going on. Temps done after a 43 mile drive, engine idling, temp gauge says 188 on the obdii port. Belt is routed same as my '98, fan blades curve is the same too.. outside temp is 57 degrees... temps driving home were between 193 and 200 (at hottest) driving through town at 35 mph was around 188 to 190