Uh oh... Thermostat Housing Blew Open

[ElNormo]

So I replaced my thermostat a few weeks ago when I replaced the coolant pump. Things were going well, until today when I was backing into a parking spot. When I got out, the engine had just begun to steam. Sure enough, an enormous puddle of coolant erupted under the engine.

It appears that the four bolts holding the thermostat housing sheared themselves. When I replaced the thermostat, I used the existing bolts. Could they have been weakened? I used a torque wrench so as to avoid over-torquing them. But they could have been pretty old.

It's been oppressively hot here lately, and I had the A/C running.

I'll attach a picture.

Has anyone ever heard of this happening? Advice?

Thanks,

Norman