first of all i would like to introduce myself, im sam from sydney australia.. ive been a reader on here for quiet a while and i used to be a poster here a while back a few years ago but i cannot seem to log in with my old accounts or i cant remember my details :S anyways.
The problem at hand is i was cleaning the dust out of my computer earlier today, decided it was getting rather dusty, which shockingly wasnt as bad as i thought, although my GPU is rather chunky Asus direct CUII ill post a pic at the botton.. anyways I have a Radeon6950 2gb that takes up 3 slots, my southbridge heatsink is rather large so its really a struggle to sit my gpu nicely on the motherboard.
Anyways the asus smartdoctor reading came upto 65-70 degrees as i turned the computer on, as the temperature was rising i quickly turned the computer off, so it may have hit 100degrees for a few seconds as i turned it off. I have no clue what i have done for this to take place my gpu had cost me $300+ 6 months ago.
The GPU has been in my computer for over 6 Months working fine
Fans are running, im not sure if the first time (after the dust cleaning) was switched on for about 2 mins when i noticed the over heating but still at the time it was around 70 degrees roughly which is NOT normal for this gpu with its huge dual fan setting.
Yes my fans are working and running i turned them all the way upto 100% speed which is probably between 3500RPM - 4000+ you can hear them running really loudly and the normal temperatures before used to be a maximum of 55degrees gaming and 35-45 standby..
I don't think you've done any permanent damage, but fixing it may be complicated. There's no standard way that those heat sinks (especially one that large) are attached. You'll have to just take the card out and try to figure out what happened and how to fix it. The other approach is you can try to see if Asus will replace the card for you if it's still under warranty.