left fan issue #2019 16" i9 MacBook Pro

Try running the Apple Diagnostic to see if any hardware issues are detected. In my personal experience supporting our organization's Macs, I find both fans usually operate at very similar speeds. I find it unusual for one fan to run faster than the other which usually indicates a hardware issue.

The unusual fan noise also indicates an issue with the fan since fans should not have any unusual noise unless the fan bearing is going bad, or the fan has become damaged, or a foreign object is stuck within the fan....assuming the noise is more than just a fan running at high speed.

Hasan_mahmood wrote:

Everything goes well,Suddenly,The left fan starts loudly with loud fan spinning noise.Remains for some seconds or some minutes and goes normal.

Also! when I close the led (sleep mode)  immediately the same thing (the fans horrible spinning with noise)starts to happen.And when I open the led,the fan comes to normal quite!

what to do plz !

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

all known to cause issues on the macOS

unplug all third party peripherals to test...

To trouble shoot further you can:

—A SafeBoot How to use safe mode on your Mac - Apple Support will sort many anomalies

Does a quick disk repair before it fully boots up, and certain system caches get cleared and rebuilt, third party system modifications and system accelerations are disabled.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

This test will tell you if third party interference; most* extensions etc are not loaded in safe boot mode.

—Test issue in another user (or guest user) account Change Users & Groups settings on Mac - Apple Support

This will tell you if it a universal issue or isolated to your user/admin account.