I see a lot of variety when it comes to people's normal idle temps and normal driving temperatures. I know a lot of this can depend on load/driving conditions/environment etc. Please give a brief description of your normal temperatures, your location, driving conditions, and your means of recording whether Ultragauge, temp needle, hawkeye or whatever.

Would be cool to know what mods you have as well.

My normal temps are 199.4°f @ idle and ~185°f @ consistent highway speed via Ultragauge. I forget what thermostat I have in right now but most likely a stock reproduction. I have a 180°f soft spring Britpart to install soon when I do the water pump and will likely post here again when it's done.

How much do our Rovers really fluctuate?

 

No fancy mods for my V8 cooling system. In England doing normal day to day driving (rarely on highway), my temps range from 182-195 with a soft spring 180 degree gray t-stat, Zerex G-05 coolant with some kind of water wetter (Redline maybe?) while monitored by UltraGauge Blue and my iPad mini.

 

Idol; 181-184
operate; 188-194

inline thermostat mod, pvc breather fix, monitored by an ultra gage hardwired.

Im in New England. So it loves this time of year, the cooler yet not Arctic weather. These temps seem consistent running an errand around town & very often I won’t use the truck for a week or 2, then hop in it for a weekend and put 3-500miles easily.

 

Idling: 168-176 (depends on if it's been run hard before idling, or if it's been cold, but it always settles between 168-176 if idling for a few minutes
Operating: 168-183 (coasting downhill on a cool morning it will get down to low 160's, going up a steep hill at slow speed for a long time it will get up to 183 or so. Never hotter than that. 183 is the highest operating temp I have seen since the inline mod).
This is in 50-75 degree ambient temps. It did run a little hotter in the warmer temps.

Extinct Inline Mod
UltraGuage Monitoring
Red Line Water Wetter
1 year old water pump
04' DII 4.6

I occasionally get the P0126 code for temp too low.

 

Idle 183 -188
Operating 183 -194 183 currently temps about 40 deg F 194 in summer 70+ F
Operating hard load 185-212 212 - 90 deg F low range long very steep grade speedo not registering 2200 RPM

Black 180 thermostat
Zerex G5
New Rad and Fan clutch
10/40 synthetic oil

Monitored on cell phone via ODB

No codes

 

OEM 180 stat, 188 on the highway, and 188-194 around town.

 

Stock everything except 180 LR thermostat. At idle and driving around town here's what I see =

Rock solid at 188 when the AC cooling fan is on
Rock solid at 194 when the AC cooling fan is not on

Minor variance with engine loads/climbing hills but generally this is what I see. It's very helpful to get to know where my truck normally is via the Ultragauge because if things spike or drop, I have an alarm set and notice. Hopefully this little gadget saves me a head gasket or two over the next few years.

 

193 Highway
200 In Town

I replaced the T-stat with a "180" degree dorman one from Autozone but based upon my temps I'm not convinced it's actually a 180 degree T-stat. Temps aren't too bad so I haven't gotten around to replacing it again, but I've also been eyeing Extinct's inline mod too.

 

Bearmach 78c thermostat
Hayden 2991 fan clutch
Spectra c15001 fan
Nissen radiator (was in truck when bought)
probably stock water pump
Filtered water + maybe 20-30% green antifreeze and bottle of water wetter

Normal operating temp 183-194, 177 low on interstate, high has gotten around 215 on extremely hot and humid 85F+ days sitting for long time with AC on. Rarely goes over 194 even after going to 5k rpm multiple times in a row lol. Never gotten any cold codes, this is probably around the lowest you'd wanna be at. This might have some issues in really cold climates, haven't tested in any place cold really, sure wish I had the rover when I lived up north though.

Would really like to get some dang hood louvers or something one day to stop the heat soak at long idle. Might switch to electric fans eventually. Actually have a cheap setup sitting in shop ready to go for when I get the chance to play with my D2. Have 2 other vehicles to finish before I tear it apart tho.

 

Based on "Power Tuning a Rover V8" or whatever that PDF is called, don't remember exactly... 170-180F is where they are the happiest for horsepower and longevity. I certianly don't think 194f is harmful by any means, but just wanted to point out that I do believe these engines were designed to run at what we would consider very cool temperatures compared to modern cars. Most thermostats were 170 or 180 degree units in the 60's and 70's before the EPA got too involved... Just my $0.02.

I put Extinct's inline mod on mine and now I rarely see 180 in cool weather. I'm confident it is in no way harmful, but I do get the "too slow to get to operating temp" P0126 code from time to time. Really only if you fire up the heater full blast before the motor is at operating temp.

I also have a new cooling system and Hayden HD fan clutch w/ Dorman fan, and run water wetter.