UPDATE:
I changed the main thermostat yesterday. Not a difficult job, just a bit tedious.
Pics:
You have to strip a few things out. Quite easy working on this car I must say.
Lots of space to work in.
First time seeing my turbo, it's really dirty and I'm surprised at the size of the thing, wasn't expecting it to be so big.
The blades are still good, with extremely little play on the shaft. Feels nice and solid and spins nice and freely.
The stuff on the inlet of the turbo isn't pitting, its a bit of dust that settled in there when I took the inlet pipe off the turbo. I cleaned it up nicely before re-fitting the inlet pipe.
Old thermostat out. Quite an easy job really.
The verdict - the temp went up to 97 eventually after hooning the car around my neighbourhood for a few kays and the radiator fan kicked in. This morning on the highway though, the temp only went up to 75 degrees. So the engine temp has gone up by about 15-20 degrees I'd say. But still not reaching 90. I'll have to get the EGR thermostat as well. Good thing I didn't get antifreeze yet as I had a suspicion that it was the EGR thermostat.