Question 1080ti 90c when idle (Update)

[mamtox]

I have a MSI GTX 1080ti Seahawk (not overclocked).
Today I turned the computer on and the GPU fan was running loud (3800rpm) constantly. I checked corsair link and the temperature was 90.0c. I was also getting artifacting on both my monitors. Clock speeds were all over the place constantly flickering from 139 to 501 to 1433 and back. All this was while Idle on home screen. Task manager states GPU usage at 2%. Card is also cool to the touch. When I turn the computer on it starts up at about 50c and within a minute climbs to 90c.
I am out of ideas on what I could do to fix this.
This happened once before about 12 months ago, however I forget if I did anything specific to get it working normally again.

What i've tried:

1. turn it off and on again
2. take apart GPU and clean out all dust.
3. update windows and GPU drivers
4. reinstall GPU drivers (by pressing reinstall button on Geforce Experience.

[UPDATE]
I have just taken apart my AIO pump, drained and refilled the cooler. I plugged in the pump to ensure it spins and works correctly (which it does), before reinstalling to the GPU.
Now I have no idea what's wrong as the pump seems to work fine.

 

[Darkbreeze]

Well, that card is about 3.5 to 4 years old. If it's been used quite a bit it's possible that the thermal paste below the water block has dried out and needs to be replaced, if you haven't already.