I also had the same problem! Google says quite a few people have been having problems with the fans although I seem to have fixed mine for the time being.
You can unscrew the fan from the heatsink with 3 screws behind the fan and then, holding the fan at 90 degress you can then take the fan off the fan base. You need to apply a little bit of force to get it off. The 1st time I done it i snapped off one of the fan fins
SO BE VERY CAREFUL!! I then applied a couple of drops of 3 in 1 oil (has to be the blue one apparently) to the centre and the rim of the actual fan. I clipped it back in and the fans seem to be working better then ever! I superglued the snapped fin back in place, although that's probably not recommended it seems strong :-/I also applied some new thermal paste and it's cooler then before too.
If you don't want to risk it and don't mind losing precious mining time then you should probably sent it back to be replaced. I am a little upset that I probably invalidated the warranty trying to fix their cheap fans.
Although it's working OK at the moment I would not buy this card again for mining.
