Not thermostat dependent. The Rover cooling system just doesn't have the capacity to get it below ambient + 100. You'd need a new radiator and possibly new fan to do better.

 

Exactly this. If you run a 170, she will run 175 if the temp is 75. If the temp is 65 she will run 170. If the temp 90 she will run 190. All examples are at 70 mph, relatively flat grade. Heavy grade or pulling a heavy trailer will be more. Idle will be lower. As DCDisco2 states, the radiator does not have the heat transfer capacity to get rid of more heat than 100 over ambient at the fuel usage at 70mph. More fuel (steeep grade) is more BTU, less fuel (idle, coasting) is less BTU.

 

@Extinct @DCDisco2 Thanks I figured that, but as it is often referenced it is handy to get the clarity.

 

Does humidity play a factor? 95 degrees in Florida. 95 in Nevada?
Intake temp of 84. Never have seen mine that low. Always in the 130’s like TimInNova is showing.
also could swear my temps go up 5-8 degrees when I have the aluminum coolant tank installed. Maybe my imagination :-)

 

Only if it's raining LOL. I grew up in Louisiana, some days it was 95 degrees and pouring rain. That will keep it a bit cooler but not much as the water evaporates off the radiator.

My intake temp of 84 was 10pm last night, outisde air temp probably 80. 70 mph speed/2500 rpm lowers your IAT closer to ambient due to shear volume of airlflow through maf, does not have time to heat up so much.

 

@Extinct big problem upper rad hose hot lower rad hose cold after switch temp hit 230 any suggestions lots of air coming out

 

I removed the thermostat and took the Disco back out onto the highway. Outside temperature was 90 degrees.

At 65 MPH* my OBD2 temp almost hit 189 F, a full 10 degrees less than with the thermostat.
Once off the highway, the temperature eventually went down to 183 and and stayed there.







*The OBD2 speed is actually 6pmh less than actual speed due to my larger than stock tires. So 59 mph is really 65 mph

 

Ok, that is more like it. That thermostat element is not behaving like it should, warranty replacement going out in the morning.

 

Ok Bad thermostat took it out temps let the engine get to 210 (15 minutes or less) dropped like a rock after start, hit 176 at idle after 5 minutes rev'd her up to 2500 and drop to 160ish fast. No rad cap on.

Not a fun fun time. @Extinct what part number do you use for the 180 so I can source a local replacement, it (the old one) does not move in boiling water 86 Degrees here

 

Wow, over 70 kits so far and two bad ones back to back, that's weird. Anyway, 2nd warranty replacement going out tomorrow. Don't worry about sourcing local, they won't have one with the bleed hole. If you really need one immediately you can use any small block chevy thermostat, just be sure to drill a 1/8 inch bleed hole. You should be ok with no thermostat for a few days. Please accept my apologies for the defective one.

On a related note to the folks on the fence with this mod, both members were able to immediately bring their temps down by removing the thermostat element. Unfortunately bad thermostats happen occasionaly, one of the benefits of this mod is you can just remove the thermostat with minimal coolant loss until you can get another one and keep driving with no temperature risk. That is not possible with the OEM system.