see this pix of the stat. https://landroverforums.com/forum/at...mostat-005-jpg

See those four holes? In a D2, they take hot water from the upper hose and feed it to the thermostat, to make stat open. In a D1, or a Chevy, etc., the stat is inside the block, so that step is not needed.

IMHO, even though you have a new stat, it may have become plugged by stuff (stopz leeksz) floating around in your system. Stopz Leekz can hang around a long time, and is always ready to seal up small openings, it does not discriminate.

Guess you could get a tub and drain coolant, inspect stat, if not the problem re-use coolant and go to plan B. Like check for coolant loss, coolant pressure test, combustion gas in coolant chemical test (head gaskets, anyone?).

Note: flow thru stat is two directions: Up, main cooled water from lower radiator hose, which does not pass up on axis, it passes out the hose headed toward water pump. Water hose from top correctluy brings hot water down, to warm up stat inside that three pipe chamber.