Temperature readings whilst driving Ambient outside was 106 degrees F = 41 C
 

All,
106F Degrees here - 41C
Connected up the code scanner to read continuous operating parameters.

Found -

1) In parking garage with A/C on and A/C fan running: coolant temp: 201F
2) Going slightly down hill around 45 MPH: temp = 197F
3) Going up one mile hill on interstate type of road - 65 MPH 1/2 throttle
Climes from 197 to about 203F in about a minute
4) Sitting in traffic - not moving - temp = 201F
5) Decent down 1 mile hill - coasting at 55 MPH: temp = 188F
6) Turn off air conditioner - temp seemed to rise actually a few degrees. May be the cooling fan working well.
7) Turn on heater.. Temp may lowered about 2 degrees and then crept back up.

Conclusion:
Since down a hill I can get to 188 Degrees F - I am betting my radiator is a bit plugged.

Or - at 106 degrees F, 41 degrees C - we are at the limits of what the Rover was designed for.

I bet if I had a more efficient or new radiator that I could have kept the temps more steady around the actual temperature of the thermostat - 190F or so.

Have to admit, before going for the motor rad thermostat that your temps were exactly the same as mine in my 4.6 03 with a new t/stat. Normal opperating temps. Mine was checked using the Ultra Gauge EM. Since going for the motor rad 180 thermostat its dropped my temps by 5-6 degrees accross the range.

Your temps are fine dude.

Yeah totally normal. 188-204F your are in normal range. 204F I think the factory thermo is fully open. Mine have sat steady at that range for 5 years now. I have changed the coolant twice and use water wetter. Its just the operating range of the truck.

On a off note. I hooked my ScanGuageII up to my girlfriends Jeep Liberty on a trip. Same thing. Stays 196-204...(Also a DexCool vehical)

A lot of people would be glad to have thos readings.