There are only two moving parts: the fan (or fans) and the hard drive. Remove the hard drive. If that silences the noise, replace the drive with a new one. If not, replace the fan with a new one.
yeah I did use my laptop without an hdd for a while and used an ssd, dont know if that makes a difference. And I tried to take out the fan, but it seems to be stuck very good. I'm afraid I might break something by using a lot of force.
Let the system run for 20-30 minutes (or use a hair dryer to warm up the heatsink. That will make it much easier to detach the heatsink-fan assembly.
You may want to have a new one ready -- if the issue occurred with an SSD installed, the fan has to be bad. It's the only moving part in the system.