previous - see https://landroverforums.com/forum/ge...ter-4-a-51028/

Chapter 5 - Thermostats

The D1 has a conventional in-the-block thermostat, about $10, same as many GM vehicles. Two bolts hold on the housing, and a Fel-Pro 12994 gasket is used. The spring side of thermostat goes inside the block. Many new stats have a "jiggle" device that allows steam pockets to pass the thermostat and not build up. The device, or any small hole drilled in the stat flange, should be mounted at 12:00 position.

Stats are available 195, alternate 180F, 160F, and some run with no stat. No stat does not work well, and usually a truck found to have no stat had overheating in the past. An alternative to no stat in the tropics is to bypass the heater core. I live in a warm area and enjoy the 180F. Stats can be easily tested by boiling in water on the stove. They begin to open at their rated temp, then open fully by another 15 to 20 F above that. Tom Rowe found this 180 stat: Fits like it was made for it. Stant Superstat - 45858 - $9.99 at Advance Auto, I crossed it from a Gates 33478S, so I expect that would work also. It's a slightly off center design with a jiggle pin (to help bleeding the air out) in the flange. Stainless steel, brass and copper.

If you allow stat to slip down when installing, it will leave a crescent shaped opening and perform like no stat at all. May not leak as flange is thin.

A D2 (and some newer Rangies) will have a remote thermostat in a housing with three openings. Cool water comes in the bottom from the radiator. Water leaves toward the water pump from the side port. The center top port gets a sample of hot water leaving the engine. That sample warms up the main stat, so it will open and allow coolant flow into the engine. The sample holes can become clogged when work is done on the cooling system, and change the operation of the stat.

Factory is open at 180F, fully open at 204 F. Owners have found an alternate temperature 82 degree C stat, the "soft spring model, and began to use it to get 6 - 10 degrees cooler operation. Some owners installed a conventional stat inside a hose box, the "in-line" option, again to get cooler runing temps. Non LR remote thermostats have some quality control issues reported by some owners, not opening when heated up.

Chapter 6 https://landroverforums.com/forum/ge...ter-6-a-51033/

 

For the D1 the factory thermostat is fully open at 88c (190F), so using what's listed in most US parts books is going to be too hot.

 

bump - update D2 stat pix with flow info

 

What would be the effect of drilling out the metering holes, making them larger?

 

As a tinkering type guy, I'd go up in small steps. It can't lower temp beyond what the wax pellet inside the stat is made for. But if clogged they can raise it. On guy did an in-line stat and drilled a couple of good sized holes in that, and the Disceo ECU decided he had a locked open thermostat and threw codes. That is where that coolant sensor on the radiator bottom outlet comes in.