I have posted a few times about my temps in the past, and am still scratching my head here. No matter what, the temps are still high. And as an FYI, the entire cooling system is new (twice over) including every hose, rad, water pump, fan/clutch, etc. It has never overheated once, and I have never had to add a drop of coolant.
So, I had a few trips this week and had about 600 miles of testing on it, mostly highway. The one thing I am thinking about trying is running without a t-stat just to see what it will do to temps. Likely not a great year round idea, but for the summer might as well. Here are a few things I have noticed, with the outside temps around 70:
Highway driving at 70: 208
Highway driving at 70 with heat at full blast: 206
Highway driving at 60: 210
Back road driving at 50: 215
Back road driving at 50 in 3rd gear: 208
Around town driving at 30-40: 217-221
Stopped at a light: 224
Stopped at a light, put in neutral and rev engine to 2200RPM: 210
So, being I can quickly drop the temp by raising the RPMs a bit, I still contend that it is more of a coolant flow/pressure issue. The stat can be opened with pressure, which is why I'm thinking the added RPMs are creating extra pressure and circulation. It is not the fan moving faster lowering the temps, as the drops are immediate when the revs go up.
Also, as a final note, the fan is in there correct and the aux fan works and kicks in just fine.
So, if I can run without one it will be a telltale sign I think. So, how would one go about doing this?

 

The title should have obviously read "without" a t-stat. *smacks head*

 

My temps are solid 95 at highway speed, around 200 +/-5 in the city with Original landrover thermostat, which I got from the dealer. LandRover also makes low temp T-Stats, used in other cars, which should be plug and play, no modification, that might lower your temps.
Here is thread with more info and links to other forums
Installed 180f thermostat in place of 192f thermostat - Land Rover Forums : Land Rover and Range Rover Forum

 

IMHO there are some other things to consider:

Has engine coolant temp sensor been changed, and is the wiring connection clean and tight? Remove sensor and descale calcium build up on it with wire brush?

You could also convert to the in-line stat, which would allow choices of none, 160, 180, or 195 stats.

You could consider the water pump with larger bronze impeller from BP Utah and others.

Heater core could also be restricted. When main stat is closed, heater core is the water path. When you come off idle, the increase in water pressure pushes down that bypass disk (one with holes in it) so heater core does not have to take full pressure. You see instant change, because flow increases. Could bypass heater core in/out as a test (hose mender kit from auto parts store - a double male and hose clamps, or at least reverse flush it. When main stat is open, bypass disk is prevented from moving down. One of the alternative stats has a "softer" spring.

You could consider the alternative stat in previous post.

With 180F stat, this past weekend (90F) I'm at 180-183 at 55, 185-187 at 70, AC on. Only hit above 200 if parked for a long period. May see 190's when in slow traffic. When I tried no stat last summer, ran 130 - 145 F with 90 - 100 F outside.

S - thanks for pix

 

You can try running a range rover thermostat to get your temps down another 5-6 degrees. And I would assume you've bled the system a couple of times at least right?

Motorad 439-180 Engine Coolant Thermostat | eBay

 

The stat will help. But the higher temps than other guys with same stock stat seems to point to additional small issues.

 

You never run without a t/stat, especially when you most likely just have a plugged up radiator. Once that is replaced if you still want it cooler, then contact Justin at Luck8 and buy either a soft spring or diesel after market t/stat and your problems will be gone.

 

Mike...look at the original. Everything is new, and nothing is plugged up. Not only that, but everything is new twice over. I will take a look at the soft spring t-stat though...might as well put number 6 in there! What I was seeing here though if there was an easy "test" to run without the t-stat and see where temps go before I go buy yet another new stat.
Buzz, I did flush out the heater core a few times now. This truck has not had Dex for what I can tell is 3 years. Heat is strong, and I have no reason to believe that is obstructed. Also, turning on the heat lowers the temps 2 degrees so I'm figuring that is working out. I might give the bypass a try though for the heck of it. Also, the temp sensor is also new, and looks to be accurate. As you know especially, the entire system is brand spanking new, with the exception of the heater core. Also, do you know the best way to reverse flush it? It has been done twice, but maybe I'm just not getting the pressure in there enough. Comes out clean.

 

By what means are you using to read your temps?

 

Ultra gauge. I never would have known the temps were even elevated without that stupid thing! The factory idiot gauge has never gone past the middle, I have never overheated and never lost coolant anywhere.