Why did my thermostat housing break?

[Bairdogg]

After a month of delay after delay on this cooling refresh, I was happy to be finally putting everything back together (except my accessory belt which arrived in the wrong size and my PS belt which I can't get off). As I was setting my thermostat housing back on, the last step before I filled her up with fresh coolant, the top snapped off.

I can't for the life of me figure out why this happened but I want to make sure I don't repeat the mistake with the new housing. I was using a torque wrench set to 82 inch-pounds, below the recommended spec. I torqued down the bottom two screws no problem. The upper screw on the passenger side (LHD) snapped the housing before it was even close to being torqued.

Some points:
-The drivers side screw was pretty difficult to thread in, even with a ratchet, but this was the same when I took the housing off after to make sure
-perhaps the new thermostat wasn't seated in all the way? (99% sure it was though)
-The top two screws appear to be longer than the bottom two? Did I mix these up?
-Did I torque them in the wrong order? They were all fully hand tight before I went around with the wrench.

Thanks guys. Super pissed right now, this was supposed to take me a weekend when I started in February but my luck is no good at all.


Sent from my iPhone using Tapatalk

[mmark.]

It becomes brittle from many heat cycles.
Only thing about torquing fasteners is that the threads should probably be chased, with a tap to remove the corrosion .

m