Haven't really found much on this.
I idled the disco for about an hour and Temps stay between 190 and 194°
As soon as I drive around the neighborhood for about 2 to 5 min it with get to 220 before I pull back into my house. Once parked and idleing it will go back down.
Not sure if it is thermostat that's stuck closed. The hose beneath the thermostat is staying cool in comparison to the rest.
Coolant has been bleed in the way I've always done it. (Filling it while cold and holding the tank above the engine till no bubbles come out of the bleed screw.)
No waterfall noise in the truck either. Heat works very well too.
I have an extra thermostat at home that I'll try. Going to field training today so I'm just posting this for any ideas on what it could be

 

OEM design can collect crap under the thermostat if the coolant isn't flushed per service interval. Change it out and slap the old one in a pot of water and slap it on the stove. Watch n see if it opens fully.

 

I could tell by your phrasing you were running an oem style thermostat, obviously I do not recommend and instead recommend the inline mod. However if you are intent on staying with the factory design I have two brand new ones I am willing to ship to you if you are willing to pay shipping. Email me if you want them, I will never use them.

 

1,000% recommend the inline thermostat swap. My 04 Disco would get high temps (220ish on my ultra gauge) waiting in the school pickup line before. After the inline swap it MIGHT get up to 180-183 even while driving. It will idle at 170 no problem.

 

How often is coolant flush recommended ??

 

@Tomzsix 3 to 5 years, I tend to 3 myself. And no additives, just dump flush with water and refill. I use tap water to flush, forward and back if you are concerned about water quality you can do a final flush with distilled.