Loud hum from fan

[WielderOfChaos]

My i5 6500 stock cooler revs up every five minutes fo about 10 secs. Is this normal.
Its completely still when its not revved up.(i took the side panel off and watched).
My mobo is an asrock z170 pro 4

 

[GhislainG]

Install Intel XTU, let it run in the background and check what the CPU temperature is when this occurs.

 

[WielderOfChaos]

I ran it and i cound that it revs when thw cpu hits 75celsius. It makes sense it would rev at that temp. My problem is that it appears to not bother cooling until then. This means my pc runs. Upt to 75. Gets cooled to 65 then warms up to 75 again

 

[GhislainG]

Cooler? Ambient temperature? Fan profile in the BIOS?