Oreilly has this stat in stock by my house. I was going to pick it up this afternoon if you think it'll be compatible?

Murray® Temperature Control Ultra - Thermostat
Part Number: 15358
Line: MCS
1 Year Limited Warranty
UPC: 799304153580
Larger Than OE Opening Allows Increased Coolant Flow
Triple Bridge Design For Added Durability
Ultrastat Thermostat
180 Degrees Fahrenheit
Alternate Temperature

 

I've not had good luck with their house brand...two failed within a year of installation (locked open).
I'd find a Stant or Gates crossover

 

put in a 180 degree stat today but still the same problem. After idling 15 minutes or so the temp starts to creep up past the midway point on the gauge. Not sure what the best next move is. I don't want to just randomly replace parts.

 

Ok, hate to admit I hadn't already done this since i bought the d90 a couple months ago but I checked the oil which was low and added 1-2 qts.

Helped a lot! Drove around for about 30-45 minutes with no issue. After sitting for 5 minutes though it heats up past the halfway mark but if I drive a bit it cools down. I'm going to flush the radiator tomorrow and see if that fixes the issue.

Thanks for the help

 

Check your fan clutch and your electric fan. If clutch is wimpy (spins more than partial turn when released and engine hot) you won't have good cooling low speed and idle. Electric fan comes on when AC on if a D1, or at 212.

 

He has a D90 so 50/50 chance he doesn't have AC.

You can try flushing the radiator, but if it's the original radiator odds are good you'll need, at the least, to get it rodded. Maybe even a recore.
The issue with rodding and old radiator that's clogged up is that often the crud is sealing leaks. Once cleaned out it begins to leak, or soon thereafter. But if you can find someone to do it for a hundred or less it might be worth a try. The cost of brass and copper have really gone up and the last radiator I had an HD core put in cost me $480. Though a D90 might be slightly less.

 

Going the old radiator is forever clogged route, while it is not copper/brass; there is an aluminum direct fit for Disco 1 and Range Rovers of a certain age, $235.

And Tom is right, old clogs can turn into leaks. Also, most home brew clean and flush methods can't get it all out, years of 24/7 chemical activity can not be erased in ten minutes. If done as preventatives, with the 2 year / 30,000 mile coolant flush (compared to 10 year 150K on an LR3); rad will be much healthier.

I thought I was so smart pulling a $50 boneyard radiator. Got it swapped in and found out the oil cooler was 95% blocked. Oil light would not go out.

 

I appreciate all the good info. I flushed the radiator out and took the D90 out for a 30 plus minute drive in town stop and go. It was in the low hundreds and I had the a/c cranked. No overheating issues!

The radiator was put in new with the engine by the original owner. The new setup has 14,000 miles but the swap was about 10 years ago. The owner was older and had an injury that kept him from using the D90 as much, but he was maticulous with his maintenance and records.

I may need to pull the radiator and have it cored if the issue rears its ugly head again. It's pretty brutal to warm up any vehicle and let it idle with the air cranked when its 105 degrees out.

I did check the fan clutch after warm up and it was good. The hand test on the radiator did show the lower cores warmer than the upper so I'll keep driving and see how it goes. Hopefully pulling the rad is easier on the D90 than my 01 DII. anyone have a repair manual for the D90. I have one for the DII and it really helps.

 

see Land Rover Manuals