Why cant it ever be easy?
 

Thought I'd do some ranting.

So a t-stat swap. Quick and easy right? Nope. Got the t-stat, gasket, rtv, etc... Real cheap for these parts. Go home, let the engine cool. So far so good.

Drain out some of the coolant. Pull the bolts, the housing, and old t-stat out. Stuff a rag in there, wire brush the old gasket and sealer off the mating surface via dremel. Easy.

Pop the new t-stat in, rtv, gasket. Bing bam, done. Tighten up the bolts fill the coolant, start her up...

...

Slight coolant leak. "Okay". Tighten the top bolt. Tighten the bottom bolt... Snap!

"Wft...?"

Inspect the housing, bolt, hoses, everything looks A-okay...

...

Start it up again... Coolant pouring out the bottom of housing.
"WTF!?!?" Turn it off and check it... Nothing seen. Back the bolts out and re-tighten... CRACK. I see it this time. Whole bottom of the housing snapped in half. Back the bolts of, remove the housing, and it falls apart in my hand.

"WTF!!!!"

Stuck in the driveway.

Ugh...

WALK back to autozone... "I need a t-stat housing". Pick one up for $13 and start the walk back home.

Unhook all the hoses, pull the old one out, pop the new one in. Bing bam, done. Wait I'm missing something... Temp sender. "Do I have the right size wrench?" "No I don't"...
"WTF..."

Out with the ol dremel... Take the socket size down on the temp sender, fit an 18mm wretch over and crank it off.

The last piece of the puzzle.

Zip it up and call it a night. Finally. It can never be easy.

sounds like the t stat fell on you when you were putting the housing back on. that will surely ruin the alignment and create a leak, and when tightened up crack the housing.

It's possible. Though it didn't appear to be the case when pulling everything off... I think I just over torqued the bottom bolt against old flimsy aluminum casting.