Blown head gasket thermostat?

so I just took the thermostat out of the car because the dealership said it stuck closed and caused the head gasket to blow. The problem is the thermostat in there was a fail safe motorad one literally can’t get stuck closed. So now the issue is what caused it. And why is it overheating. Just another discovery in owning my SHO

 

Dont they need oriented correctly with the jiggle valve up or something? Or is that just a myth.
Quick internet search shows many failures for stuck closed on multiple types of vehicles with that thermostat.
No such thing as a fail safe thermostat, it would just have a lower failure rate or a higher fail rate because it jynxed itself

 

I thought there was such a thing. On my GF’s 14 Jeep Grand Cherokee they say the thermostat will fail open and thus it still protects the engine. We thought maybe she needed one, it threw a code for it but the fluid was extremely low, just from filling it back up after 3 days of drive cycles it cleared itself and the level is holding, so don’t think it’s leaking either. Honestly I think the garage we brought it to a sabotaged it....bc I had recently did the brakes and oil change and topped off all her fluids, only thing I needed to top off was windshield washer fluid....then shortly after we got it back the radiator fluid was bone dry? Yeah....nice try shitbags!

 

That's correct as far as my replacement memory goes. I think there may be more than 1 design and the jiggle valve one is preferred and valves up.

 

I never really thought about it but how does the jiggle work. Does it let coolant through in the event of a closed thermostat? Does it allow air bubbles to move up when in closed operation when cold?

 

I think it might be for gas pressure. Probably allows for some coolant too but the openings are very small. Not like a wide open larger valve. I keep forgetting sometimes I'm posting in the newer car section. My previous post is in regards to the older cars. Here is a rando google pic of an example. I forget if the ones I used had 1 or 2 of those little jiggle valves on it.