How to clean MBP 2011 Fan?

You can try running the Apple Diagnostics to see if any hardware issues are detected.

The fans running at high speed can be due to a temperature sensor not working correctly. On such an old laptop a bad battery could be why a temperature sensor is not seen since the battery has a built-in temperature sensor.

Also, there may be a possibility the fans could run fast if there is no OS since there is an OS component to the fan operation.

If you get a "recovery server could not be contacted" error message when trying to install High Sierra, then try Fix #3 in the following article:

https://mrmacintosh.com/how-to-fix-the-recovery-server-could-not-be-contacted-error-high-sierra-recovery-is-still-online-but-broken/

Edit: Forgot the link to instructions for accessing the Apple Diagnostics:

Use Apple Diagnostics to test your Mac - Apple Support

Also, I just realized we forgot to mention trying an SMC Reset:

Reset the SMC of your Mac - Apple Support

alman240 wrote:

I need to clean my Late 2011 MBP's fan because when I boot into recovery, the fan goes really loud (NOTE: There is no OS on it.) I don't have compressed air or a vacuum.

It sounds more like a hardware issue, not a dirty fan.

The RPMs are ramped up—A loud fan is not going to hurt it.

It begs the question —why is there no OS on it? Does it proceed or the OS is no longer available?

restart your Mac and immediately hold down the Command-R key combination to start up from macOS Recovery?

The older macOS installer backups:

How to download and install macOS - Apple Support

alman240 wrote:

It doesn't have an OS because I didn't use it anymore, so I erased it but I want to use it again for experimenting.

The older macOS installer backups:

How to download and install macOS - Apple Support

ref: High Sierra 10.13.6

Create a bootable installer for macOS