The laptop cooling fan makes a rattling noise. The noise comes and goes.
1. Something stuck inside the fan.
2. Fan failure.
Possible troubleshooting steps and repair solution:
First of all, make sure it’s not the hard drive noise. In some cases, a faulty hard drive can make noises very similar to a faulty cooling fan.
Take a look inside the cooling fan under a bright light. It’s possible that something got stuck inside the fan and prevents it from spinning freely. You can remove a stuck object with needle-nose pliers.
Try cleaning the fan with compressed air.
If there is no stuck object inside the fan, most likely the fan has a failed bearing and has to be replaced. Replace the cooling fan if needed.