I have a bluetooth gauge that plugs into the OBD2 and connects to cell phone wirelessly. Noticed that on the freeway my temps run about 206-210. Once I exit the temps will climb to 212-215 (highest) aux fan will start running. We were coming out of a valley up a moderate grade dropped it to 3rd got the RPMs up and the temps dropped to 197-199. Keep in mind the temps outside never got about 60deg.
Is it normal to see temps drop at higher RPM (seems backwards to me) and stay low. Instinct tells me clogged/plugged radiator. Thoughts? Or is this all normal? (BTW I have a new water pump and new thermostat (not grey))

 

Higher rpms = water pump & clutch fan spinning faster. Won't make much difference at highway speed, but could if you're slowly making your way up a hill.

 

What phone app are you using with your bluetooth OBDII device? Also, go with the grey LR T-stat or the Motorad 180 T-stat you will be happier and your D2 will as well!

 

I would go with your instinct about sludged radiator. One test is to check the temp from top to bottom on the fins using an IR thermometer. Looking for a spread of maybe 10F. If higher spread - sludge fills up the lower passages, and they will be cooler (less water going thru them, if at all). If you replace rad, also get that 180F stat soft spring stat.

 

Reporting back-

Finally got around to working on the rover. Took the infrared gauge and the spread across the radiator would vary by 20+ deg. The middle was cold. Based on the heat readings the coolant was flowing around the perimeter.

So, replaced the radiator and thermostat with the warm weather one (grey). Temps are now in the mid-high 190's vs. 206-212....much better. I took the old radiator apart and could only see daylight through half of the channels. Appears something gritty (sand?) is plugging up the channels.

 

You are running to hot for this time of year. When was the last time you tested your viscus clutch?

 

It looks like sand but instead of silica it is calcium, cooked out of water that had mineral content. Distilled water is best, or use 50/50 premix coolant, and change every 2-3 years. Well water is worst, can have high mineral content. How about some pix of the problem?

BTW - good job. And that "cold in the middle" can make the air flow in that area cooler and keep the viscous drive fan clutch from operating as it should. But be sure to test it for mechanical operation by spinning when cold, then again once engine fully warmed up. Should not spin more that 1 turn when released, freewheeling indicates loss of silicone fluid inside clutch.

 

Good job!

 

Nice find/fix, glad you got it worked out.

When you swapped out the new stuff did you convert over to the conventional green coolant and ditch the Dex / OAT orange coolant? That crap loves to mess with these engines/components.

My DII should be back on the road soon and I replaced most of the cooling system, including the new motorrad tstat so I'm excited to see what the new temps will be - I had seen fluctuations and aux fan activation at odd times before the resto as well.

 

Glad you got it fixed! But, like Disco Mike said, 190s still sounds hotter than normal, unless you're in the middle of the desert. Here in Georgia with temps in the 50s my D1 with a 180deg thermostat barely gets up to 170 sitting in traffic.