I'm confused.

I bought a thermostat from Autozone to replace the one that I have because it was all broken up and besides..I'm replacing the radiator today. Anyway...I want to be sure I'm putting it in right because the car ran hot after I had finished the radiator replacement (of course filled with flush + water). Which way does the thermostat go in? Does the thermostat have to have one of those little jiggly things? (this one doesn't). Does the spring part go down towards the engine? Someone told me that there's only one way that the thermostat will go in; however, the one I have from Autozone will go into the little housing both ways (of course with the o-ring). Help this confused man.

It goes in with the coil spring into the engine. Kind of surprised that there's no little jiggly vent thing, but then again Autozone never surprises me when they don't have exactly the right thing.
Note that you don't NEED any sealant if the surfaces are all clean. If it's crusty, clean as best you can, and I use a thin coat of blue silicone RTV. It can't hurt and it does come off easily enough next time. Really the key is getting everything nice and clean.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 225K, 88 744GLE- 209K, 91 244 183K. Also responsible for the care and feeding of: 88 745GLE, 229K, 88 244GL, 146K, 87 244DL, 235K, 88 245DL, 236K

That's how I installed it; however, the top radiator hose stayed very cool and the temperature gauge was headed up Mt Everest. Afterwards, I removed the thermostat and ran the car w/o a thermostat and everyone was happy. The temp gauge was at like 7 o'clock. So I KNOW it's the thermostat. I just bought the darn thing. Why won't it open..huh.

Sometimes after a cooling system drain down there are pockets of air trapped in the block. In general, you have to refill the block by pouring coolant awkwardly into the hole under where the 'stat sits. Fill until you see coolant. Button everything up, then fill the rad via the top hose (disconnected at the 'stat), and top off via the expansion tank. Sounds a little anal but I've never had a problem after I refilled this way.

However, now your system has 'cycled' a couple of times, so there should be no air trapped on the engine side of the 'stat. Check the 'stat in hot water per other posts, and if its OK, reinstall it (drain down the radiator a bit first, with a cold engine), then top off coolant thru the expansion tank.

Take the thermostat, suspend it by a wire in a pan of water and bring the water to a boil. Check the water temperature with a cooking thermometer. You can see if the thermostat starts to open at the marked temperature. This is kind of interesting to do as you can see how a thermostat works soooo slowly.

Cool!! I did it. I lowered the spring end of the 'stat into the hot water and the thing opened up. It was pretty cool to see. Anyway...I'm pretty sure the only reason the darn thing didn't work the first time I installed it is b/c the engine block wasn't topped off in water (had some voids in it). I'm gonna re-install and be very aware of not draining the whole system again. It was the radiator replacement that caused me to drain the entire system the first time. By the way...if this transmission holds together I'll be surprised....this is a case of replacing a ruptured tranny cooler. We've flushed it out and everything...we'll see.