I was going to do a post on this. I will later.
I think the gauge is actually a 6 position gauge, but the normal, and high but normal indications are so marginally different, that they look almost the same. LR obviously programmed it that way so people don't think about it unless they have to think about it.
From what I've seen the dash uses these 6 positions:
- Cold - needle at the bottom of the gauge
- Warmed up but still cold (my stuck thermostat ran all the time at this position) - about 1/4 of the way up. The D2 Td5 cooling system has a huge amount of capacity.
- Normal running temp - in the middle, water waves are just under the needle.
- High normal running temp - slight gap between under the needle and the water waves, electric radiator fan stays on, then later AC goes warm
- Hot - 3/4 of the way up, throttle will only give idle
- Actually properly hot - Needle to the top. Red light comes on. Idle only.
Because it overheats, it isn't necessarily damaged by the heat, but something needs fixing.