Now I've seen two different videos of a XC90 3.2 with a failed Thermostat.
In the second video a 2008 3.2 has a failed Thermostat and based on the marking on the Thermostat it looks like the broken part is an aftermarket part. If the original part lasted about 10 years (a typical lifetime) then the aftermarket part only lasted 3 years.
Conclusion: this is one of those parts that the factory specification exceeds the aftermarket replacement. Also the failure mode appears to be the seal and not the plastic. I replaced my 2008 LR2 3.2 Thermostat at 10 years (preventatively it was working fine, not leaking, and still intact upon removal) and I don't plan to replace it again until 2028 when my SUV is 20 years old.
Note: the 3.2 used by Volvo and Land Rover was built in the UK at a FORD Engine plant and the engine is nearly identical (Ok the LR2 is more like the S80 than the XC90 if you know the differences between S80 and XC90). Which is why I use a Volvo or Land Rover Thermostat which ever is cheaper. When the engine was made it used a FOMOCO thermostat. Now you can buy that exact Thermostat in a Volvo box or Land Rover box.
Don't buy cheap aftermarket Thermostats for the 3.2 or 3.0T.
Note: the surprising thing is that the failure mode appears to be non standard. And based on the second video the failure seems to be very premature (How is that XC90 on Thermostat #3 at 13 years old?).
Common failure mode for 3.2 Thermostat
1. Cracked plastic due to return spring shear force and thermal cycles (Fatigue or Creep rupture is the likely phenomenon)
2. Plastic failure of the O-ring groove at its thinnest section
Mode #1
Failure mode #2
Arrow point at location of the failure, I'll search the internet for the picture of the failed part
New Failure mode
Conclusion
I would need to get a closer look at the actual part to confirm but it appears that the plastic housing has deformed due to heat. Two possible reasons.
1. the coolant leaked out and engine got very hot and this warped the plastic
2. an aftermarket Thermostat was used and it was built with an inferior plastic
Beware of aftermarket parts for components like this.
Here is the video
Thanks
Paul
Recommendation
Get the Thermostat in a Volvo box or Land Rover box.
Don't buy aftermarket.
And change it every 10 years.