Just fitted the hybrid kit to my 3080 XC3 Black, and whilst working fine for the first 20 minutes, it now makes a really loud noise every time the pump and fans comes on, and the noise remains until the fans and pump stop.

You can see this (and hear it!) here: youtu.be/VVW4CuhcKQg

Any ideas what's happening? Does it sound like there is no water getting to the pump?

The box was damaged on arrival through the post, so maybe this kit was dead on arrival, but it worked fine for 20 mins before this started.

All very disappointing :(

Yeah that sounds like a cable hitting the fan, maybe you routed it incorrectly when laying down the pump.

I just thought I'd post my overall experience of installing the the hybrid kit on the XC3 3080 Black in case anyone else finds it useful.
 
The actual installation of the kit on the card was fairly simple and the instructions provided by EVGA are reasonably clear and I never found my self stuck at any point. I did follow a video online as well just to double check I read the instructions correctly in each step.
 
Others may find the video useful:   youtube.com/watch?v=TKDQiHOs9GQ&t=878s
 
The only nerve-wracking bit was pulling the stock cooler away from the card after removing all the screws. The thermal putty had a good grip and some gentle force was required to separate the card.
 
I got caught out with installing the card into my case with one of the radiator fans becoming disconnected (its a SFF case and it's a little tight in there).  This resulted in the one plugged in fan running at 100% all of the time, and the fan controls in Precision X1 not doing anything. Once I plugged the disconnected fan back in, both fans behaved and responded to the fan controls in Precision X1
 
I then followed guides on these forums to update the bios to a hybrid BIOS. Downloading and installing the hybrid BIOS provided by EVGA_JacobF:
 
3080 XC3 HYBRID Kit BIOS = evga.com/EVGA/GeneralDownloading.aspx?file=3080_XC3_HYBRID.zip
 
 
Like others mentioned, whilst this worked, and Precision X1 was now showing the card as a Hybrid card with 2 fans rather than 3, GPU-Z was now showing an idle power draw of around 180 watts. The idle temps were in check though at around 28 degrees, suggesting the reported power draw was incorrect.
 
I read comments like "Look for the 3080 xc3 ultra hybrid BIOS on techpowerup. It will show the BIOS that comes stock with the hybrid cards from factory. That BIOS fixes the issues plus shows the card correctly as a Hybrid card".  However I was unable to find this BIOS on the techpowerup site.
 
I did eventually find it, although it is marked as an unverified BIOS:  techpowerup.com/vgabios/227530/227530
 
 
This download is a ROM file through rather than a executable. As a result, you need to download the latest version of Nvidia NVFlash and use this to flash this BIOS file.
 
Now everything look great, and the power draw figures are fine.
 
precision X1 now thinks the card is a 3080 XC3 Ultra Hybrid, even though the card is actually an XC3 Black (not an Ultra) but I haven't had any issues so far.
 
The card now runs much cooler and much quieter when compared to the stock cooler, so overall, definitely worth  it.
 
Hopefully this information helps someone.