Most gpu failed starting with the fan not working without you noticing. It is probably due to dust accumulation. If you have done proper de-dust for your case and care for your gpu fans with removal of dust balls, it should be fine. Just take note to use a long object to hold the blades (prevent bearing damage if you are blowing it with air cans or other blowers.
If it is fan failure, you can always go for after market gpu cooler.