geordi wrote:
Ok... I think I'm either getting closer to understanding the thermodynamics of this, or the rum is helping me THINK that I am.

Looking at this image, I can see how the thin peg at the top of the TS would apply physical pressure to the fixed housing as it lengthened from heating. Is the upper disc in a fixed position in relation to that peg? Meaning - As the peg lengthened, THAT is what pushes the upper disc down and opens the outlet? If that is correct, then the large diameter spring... Isn't really doing much?
As for the lower disc, is that also in a fixed position in relation to the center shaft (which seems to be a different piece than the upper peg) so that as the center expands, it "rides down" into the sealing surface...?
Sheesh. Masters of Fine Arts and a college professor... And I feel like a blithering idiot for not being able to conceptualize the operation of something that has existed on vehicles for 80 years.
Ok, I think you are getting it. The upper disc moves away from the housing. The large diameter spring holds the tstat against the water outlet and keeps water from going through the radiator at closed tstat condition. You can't see in this pic, but the 2 flanges that stick out on the side are mounted in the middle of the housing. The lower disc is in a fixed pos compared to center shaft and the lower spring absorbs movement after the port is blocked adn the piston is still moving the tstat down further. The jeep tstat is not the traditional one you see in vehicles. On the Stock jeep tstat - The piston at the top is moved out by the expanding wax inside the brass cylinder and pushes against the housing iteslf. This then puts pressure on the water outlet housing itself and pushes the whole assembly down, away from the waterneck allowing water to flow from engine to radiator. As the tstat opens, the bottom flange of the tstat makes contact on the bottom of the tstat housing and seals and blocks off the bottom port back to the engine so water only goes from engine back to radiator at open tstat condition.
Ok, See photos below...the side wings I'm gonna call them rest in those little groves. This is how the large spring pushes the tstat in the closed direction...this force is overcome by the piston movement. 

On my setup - The tstat opens by a piston pushing on a bar that goes across the thermostat iteslf (no pressure on water outlet housing like factory design) allowing the thermostat to open. As the tstat opens the lower disc gets pushed down and approaches the seating surface to block the lower port.
Piston pushes on bar going across the tstat on my setup:
So the only real difference is the stock jeep tstat pushes against the housing instead of a bar on the thermostat itself and the fact the factory tstat has a bit more travel capabilities. Thus we need to modify the bottom port so the thermostat can reach adn achieve full block-off during open tstat condition. See below:
Piston pushes against housing on factory setup:

Hope I explained this right...lol its is a bit complicated when you can't hold the parts in your hand.
