I've had this ATI Radeon HD5870 from Sapphire for about three months now, and it's run great up until two days ago.
Out of nowhere the fan started this loud, grindy whir, only at low fan speed (maybe 20-35%). I've heard rumor of fan problems being a common occurrence in some of the 5000 series.
I couldn't handle this noise, so I jacked the fan speed up to 80% and left it there while I played TF2. Since then the whirring has been intermittent, but I've noticed I'm starting to get brief screen tears or jumbles (not really sure what to call them) just after loading a webpage... oddly specific symptom I know, but it started around the same time.
I did take out the card to try and clean the fan out, but it didn't solve the noise.
Currently the GPU is running at 54.5 degrees C at idle (24% fan). It's been mostly quiet since the initial episode, but it's recurred once or twice.
I'd just like to know if the graphics glitch I'm getting in the web browser is indicative of anything, whether I should just ignore it, be worried, or what.
On the Sapphire page, the warranty section mentions a two year warranty through the vendor on all Sapphire products, yet newegg says my warranty is expired.
drop a little bit of mineral oil or other non conductive machine oil into the fan barring and anywhere else its making contact. that could help with the noise, make sure you watch it, because if the fan is gonna die, you wanna know the second it does.
You could try reinstalling drivers too, the graphical 'artifacts' could be caused by corruption. Usually its due to overheating or a defect, but a good first step to try.
Since you've cleaned the fan that step has already been taken. Try running at a slightly different speed maybe? just try to monitor temps while gaming before & after and note when the problem occurs. If its at high load/temp, its possible the fan is defective even if its operating.