OK I haven’t had to do this with any of my RPi’s….yet. But this is a cheap way to add a fan too cool off the RPi. Not so sure about it being a temp fix (I can see this changing for a permanent fix). Only issue, its not easy to find an old PC fan that is 5volts. Most I know of are 12v.
http://lifehacker.com/cool-a-raspberry-pi-with-an-old-computer-fan-1736963651