Question Component whirring down as if PC was turning off

[pcproblemguy]

The past week or two something inside my system has been whirring down as if I just turned the PC off, I've took a look at the front fans when this happens (every 20 minutes or something randomly) and I can't see any noticable difference in RPM.
My GPUs fans don't turn on over 65c or something so I doubt it's that (plus have seen them stationary when this noise happens), only thing I can think of that I can't really test is my PSU. Is there a software like HWINFO64 that I could use to check fan speed of the PSU or anything?

It's like a humm down to idle, then I hear maybe a fan kick back in or something, there's 0 power loss, no performance loss I'm just stumped at what it could mean/be.

If there's any other info you need, let me know.

CPU - i5 9600k 4.2ghz / Corsair H100x Liquid Cooler
GPU - GTX 1070 8GB
MB - ASUS® PRIME Z370-P II
RAM - Corsair VENGEANCE DDR4 2400 16GB
PSU - Corsair 750TXm Series

 

[Lutfij]

You could roll a sheet of A4 paper into a tube, then hold one end to your ear while the other end inspects for the source of the noise you speak of. How old is the PSU? If you suspect it to be the PSU, remove it from your build and then inspect the fans behavior with regards to your system's load(or at idle). You can likewise source a donor PSU and see if the same issue crops up.

Fans for the cooler maybe the source? Could also be the pump block for your AIO.

 

[pcproblemguy]

You could roll a sheet of A4 paper into a tube, then hold one end to your ear while the other end inspects for the source of the noise you speak of. How old is the PSU? If you suspect it to be the PSU, remove it from your build and then inspect the fans behavior with regards to your system's load(or at idle). You can likewise source a donor PSU and see if the same issue crops up.

Fans for the cooler maybe the source? Could also be the pump block for your AIO.

I'll give the listening with a tube try, the only thing is how unreliable it is to happen it would seem, I did have my phone under the PSU recording upwards but I've not heard it since.

The PSU is about 3 years old with daily use of avg 10 hours. This noise can happen either under full load or at idle, I do think it happens more often at full load.
Fans for the cooler would be the front fans, there's only the two of them mounted to the radiator and I don't think it's those.
The AIO pump block does have issues with powering on properly, sometimes the PC will boot with a CPU fan error and I fix this by tapping the block with a screw driver to get the solenoid free, or y'know, whatever it is I'm freeing.

 

[Lutfij]

I think your issue might be a build up of dust...coupled together with an AIO that's either cavitating or is on it's way out. Use an air cooler and see if the fan error comes up again.