After sleeping on it, let's consider how they might produce this offset.

They want 10 degree C change when outside air is cold.

They add it in the program, but at a point that not only moves the gauge back up slightly, it also skews the ECU output to OBCDII for coolant temp. Our coolant temp reads about 16 F warm.

How did they determine "cold outside air"?

IAT (Inlet Air Temp) sensor? On a D1 it is in the air box, on a D2 it is part of the MAF. Now I am not about to suggest replace that, but look at the attached page. If the IAT was unplugged, that is sensed and a default value of 113 F is used. Certainly that would not be cold outside trigger. But, if the connector was oxidized (dirty), it could increase the resistance, and make the sensor show in the "cold" area. On the attached page, on the curve, if resistance increase, temp decreases.

I suggest you use the Ultra Gauge to examine IAT, with vehicle not running, and not having run for hours. Does IAT equal outside air temp, or is it colder? (might be warmer if engine still warm). What ever reading is, note that. Turn off truck. Unplug MAF/IAT conector, and clean pins with contact cleaner or small wire bush, re-install and test temp again.

If above works out, would explain the 16 F or so high readings. But if that was happening before you barely missed an eye injury (we are damn lucky that plastic did not fly loose when you were first checking the new fan operation - and how many of us wear eye protection at home under the hood for a moment????) - if this was happening back then, wonder if it made mixture richer and cut fuel mpg? I would suppose not, the engine probably does not offset the IAT for injector control purposes.

If this works out you will have lifted the knowledge of all D2 owners. If not, maybe coolant sensor after all.

 

The AIT is a temp I keep on the display, and yes, it looks about right usually on cold start up.

 

If it makes you feel any better I have the same issue - my 2004 runs about 194-197 on the highway, 208-215 in the city, and idles around 220-222. I thought this was hot and had things looked at. I found out that my 5 month old water pump (installed by previous owner) was already leaking just a little, so I decided to replace it, the thermostat, the fan/clutch, radiator flush with 50/50 green stuff, etc as you did. No change whatsoever - truck still runs just as hot as before, so I am just living with it. I thought maybe the temp sensor may be off a little as well, but have not had the time to dig into it yet.

Let us know if you discover something!

 

Will do. Mine seems to be even a bit hotter than that, and doesn't really go down on the highway much.

 

Well, when I first sat in the truck I thought once again I found the smoking gun with the AIT:

But, once I started the engine it went to normal. Outside temp during this was around 42 degrees. I figure the old reading was the last it saw when I shut the truck off. This all looks about right:

 

I had just heated it up again and all the temps on the gauge appear to be normal for the ambient temp and AIT. Everything else seems normal as well. Heat feels fairly even across all hoses, with the exception of the lower rad hose. Later on when it cools off I might swap out the t-stat to the old one and check again. If that fails, I suppose I will buy the temp sensor.
Question about the t-stat: Are you supposed to hear a rattle inside, like a small ball bearing if you shake it? Both the old and new one had the same rattle so I didn't think anything of it, but I'm searching for *anything* right now that could be the culprit!

 

Many thermostats have a "jiggle" device that is inside a small metal hole. The hole is made to be sure air bubbles can pass by even if stat is closed. The jiggle gizmo tries to keep Stopz Leekz sealer and other trash from closing up that function on the stat. If you poured water in from one direction (not sure which) should be a trickle coming out other.

 

Figured as much, but this is the first vehicle with a t-stat like this I have had so figured I would ask. Just trying to find ANYTHING! If it is not the temp sensor, it has to be the t-stat. Everything else just seems to be 100%. I've been questioning all my work on it too, but just nothing that stands out.
I'm wondering how to test out the old t-stat in the house. If I bring water to boiling and pour it in the bottom, it should open and come out the top, correct? Cold tap water should just make it dribble out, right?

 

Just tested the old t-stat and it is OK. Putting tap water into the top two holes only allows a dibble out the bottom. Putting tap water into the bottom does not allow flow thru, only flow thru is the top and the side to pump. Putting water from the tea kettle into the top for a bit, then flipped it over and poured the kettle water into the bottom and it flowed right through.

 

see https://landroverforums.com/forum/ge...highlight=soup

your test sounds good.

As for your work, kind of hard to put radiator in upside down, etc. Water pump can be screwed up if you left in a shop rag, but usually the problems revolve around did not seal up good, wrong length bolt problems, belt route wrong.

Guess you could take out coolant temp sensor, warm gently with a hair dryer, or coffee cup of hot water, leave connected, see what it reads vs an IR thermometer.