Think about a pan of water on the stove. The burner is so hot it will burn your hand. But it still takes time for that water to boil. So to get rid of the engine heat, the water has to be inside there long enough to soak up the heat, then in the radiator long enough to cool down, then repeat. With no thermostat, under certain conditions you are heating the water faster than it is cooling off, so engine temp gets too high. And under certain conditions you are cooling it off faster than the engine is heating it up.

This is where the thermostat comes in, and keeps the engine withing a range of temps, from about 180 to 200 ish.

And Rover, following the British principle to "keep calm and carry on", makes the heat gauges slow to respond or outright liars. In the D2 as an example, the gauge is sent a signal by the ECU to maintain a 50% reading, over a range of about 130 - 240F. The D1 uses an analog gauge, with the time constants set to provide a similar dampened result. So owners of in-warrntyunits don't waster the service department's time. But owners of older units don't see that temp rising higher each week, until they have an "event". So they drive around cooking the engine as if slow roasted over hickory coals.

Now, I like the idea of knowing that you can bypass the thermostat in an emergency and drive it to get home, or maybe even until next paycheck. But decent thermosats are one of the cheapest parts you'll have to buy for a Rover. And the thermostat is not dumb, it changes how fast it cycles across the "sweet spot" for engine operation, and when things get too warm (long uphill climb, waiting in the drive thru in August) it will open and stay open, allowing maximum transfer. The electric fan comes on to help with that. The viscous fan clutch engages at higher power to help with thta. All while you remain in air conditioned comfort , salivating at the thought of the triple bacon bourbon burger and onion rings that will be yours is just a few more minutes.

The radiator is hard to "see" if it is clean, without taking apart. Most rad shops won't pull off an old brittle plastic side tank. The scale and calcium builds up inside the rows, choking off the lower ones first (gravity always wins, even with humans), Throw in some stop leak that plugs it off more, or coolant that makes sludge (Dexcool), or use well water or non-distilled water, and more build up and less heat transfer. Usually when you find a truck with no thermostat, it means the previous owner had an overheating problem that was not solved.

I think that using different instruments is great, and the idea that you can bypass the thermostat if needed is a good short term work around. But you really need the cooling system to have all the parts to work well. Using a 180F stat reduces some overheating issues Rover brought on by going to the higher temp stat to help control emissions.

Sorry to hijack, but that made me laugh. I started out majoring in aerospace engineering. Junior year I start upper level classes and take thermodynamics.

First night of homework is 5 problems. No big deal, right? Well, after almost 2 pages of math I got the first one done with no clue if my answer was even correct.

I switched majors to computer science the next week.

Back on topic...

Why does this thermostat hack job work?

https://landroverforums.com/forum/di...ck-read-29369/

Does it restrict flow enough to still cool the coolant?

The D2 remote stat is a bypass stat. The top disk descends on the soft spring at idle, to allow just hot from engine coolant to enter the main chamber, out the slots at the bottom, into the double wall area, and out the "arm" to the water pump. So passengers get heat a little quicker. As main stat opens, it forces the disk back closed, and main water flow takes place. The disk also has a series of holes that always allow some "just heated" coolant to enter the main chamber, warming up the main stat so it will work. What a great design that those holes are at the bottom of a pipe run, so gunk can collect on them and change that metering flow....

By hacking out the innards, he has basically made it an open stat. Perhaps the cross section is just right in some conditions. Before members grabbed on to the 180F stat, the other work around was the in-line stat, where you used a conventional stat in a remote box, which still works great, probably better than the 180F soft spring, just more plumbing. Too cold an engine makes oil not perform as well, higher wear. Too hot and oil thins out, higher rate of wear. Fuel MPG adjusted by ECU based on engine temp, richer when colder. So too much gas, which will wash past rings into oil, and poor oil performance, and sludge happens.

The other issue that has been touched upon but not explained in $$$ is that running rich due to being too cold will clog up your Catalytic Converters. I don't know if you've priced them yet, but believe me, you don't want to have to replace those. I had that issue with a stuck open Thermostat in my wife's VW Beetle. California Mandates you buy an OEM Catalytic, so it's a measly $900 + Tax. And the VW only has ONE, the Disco has TWO.

EDIT: Secondly, it seems like an argument each time someone offers insight (even Decades Long Veterans). I would imagine eventually, they aren't going to want to offer any more.

Good catch on the CATs. But all the back and forth on our forum will provide noobies great background material, once they learn to use the search button. And I don't think we will ever settle some arguments, like best coolant temp, best oil brand, best viscosity, best filter, best brake pads, best battery, best air filter, best tire, best shock, etc.

Only the latest modifications will improve results, and if you believe all the claims by various products, add them together and you will have the latest Rover performance, soaring over the Serengeti instead of just crossing it overland, and hoping you have run-flat tires....

The Air Rover!
https://landroverforums.com/forum/at...-jet-plane-jpg

Is there a writeup on how to install the 180 t-stat?

Same as the OEM one, has three openings.

http://ecx.images-amazon.com/images/...L._SL1500_.jpg

Or seach for in-line thermostat to see the option for adding hose, and external stat box, and your choice of stat.

I'm glad this thread is here. I just installed a 180 thermostat in my 2000 Disco II, and according to my Accutron I am hitting 199 to 201 at 55 mph, 74 degrees ambient. That seemed high but sounds like all is good. Thanks for a thoughtful thread.