I think try using a driver Uninstaller and clean installation can fix these kind of things most of the time.

have you changed the fan curve at all?

My XC3 runs hot inside Node304, but I find a way to lower its temps to 74c and no noise. 
I modded the case with 2x 120mm outtake right in side of the card where the hot air cames out.
 
I will try some different aproaches using the Coolermaster Nr200p and see how it goes... 2x 120 intake right next the gpu fans and 2x 120mm outtakes as I did in Node304. 

ctn2mb
have you changed the fan curve at all?

Running the default fan curve. With it set to aggressive I get in the realm of 45-50s 

chamm2142
Just a thing you might also check: use NVidia's GPU Activity tool to see what is using your GPU in the background.
 
My XC3 was also getting hot running at above 1700MHz without downclocking while idling on the desktop with no application open.
 
Then I used the GPU Activity tool from NVidia's control panel to see what is actually using the GPU so heavily (use: Open NVidia Settings ->Top Menu -> Desktop -> Check Display GPU Activity Icon in Notification Area).
 
Turned out that I had installed NVidia Broadcast and it is constantly using the GPU at full speed. After I uninstalled it the GPU downclocked again normally.

 
This is the winner! I just realized my GPU never downclocked at all, 1755MHZ at all times. Just did what you suggested and I went from a toast 60 degrees at idle to a nice 40 degrees!

OP if that is anything like the lancool2 case I would use the room over the PSU to mount two fans as you have intake vents in the side of the PSU shroud. I’ve got two 15mm 140‘s in mine and cooling is good

RandomSanity
P.S. Am I the only one that finds it odd that this card has no screws to keep it stable? 

What are these stability screws you speak of and what/where would they screw into.

 your temperatures are normal 

My experience is that my 3080 XC3 Ultra only gets to 75C with stock settings...  with an undervolt for performance it does get into the lower 70s because the ramp up of the stock fan curve seems to target 75C.  Furmark testing gets up to 75C (averaging 74C) stock and 72C at my undervolt of 1920/906mv.  Temps drop quickly to 50C then fans go all stop after load drops.  If you haven't, download the latest Precision X1 and update your BIOS though.
 
Similar fan layout to the original post - 3 exhaust (1 rear, 2 top), 2 intake (2 front) - all 140mm, and a Noctua D15 CPU cooler cooling a toasty 9900k on top of the card.  Half of one of the front intake fans is supplying air to hard drives in the lower shrouded area of the case too.  If you case is really starved for air (front mounted AIOs in smaller airflow restricted cases are the worse offenders) though I can see why the card might get to 80C.
 

RoyalMuffin
Recently just scored a 3080 XC3 Ultra from microcenter and despite being a beast in gaming should I worry about its thermals? On Idle the card is around 60-66C and then on load the card runs around 77-83C. This is on the default fan curve and with a more aggressive on I can get it at 77C at around 90% fan speed at load. 
 
Below is a pic of my current fan setup. There is a missing fan because I am waiting for my new corsair fan to come in. When I did the testing I had all corsair fans and one fan that came with the Lian Li case where the missing fan would be. All fans are 120m
 

My XC3 Ultra also ran hot into the 72C-74C range on an O11D-XL stock full of fans including 3 blowing cool 22C ambient air from the bottom directly into the card. XC3s run hot. When disassembled the card to install the hybrid kit, I noticed one of the thermal pads for the power delivery was not making as strong contact as it should, and the thermal paste on the GPU was already pretty dried up. If you feel comfortable with disassembly, you could try repasting the card with good quality paste like Kryonaut. Also get better thermal pads, the included thermal pads are one use only. You could loose a few degrees going this route.  It will not void the warranty and you can use the instructions from the hybrid kit installation PDF to disassemble the card safely. 
 
You could also consider buying the hybrid kit. My temps lowered significantly with the card running in the 55C range now and with a modest +125 on the core it boosts very close or stays at 2100mhz most of the time. You definitely have the radiator space on the front of the case.  

selarom

RoyalMuffin
Recently just scored a 3080 XC3 Ultra from microcenter and despite being a beast in gaming should I worry about its thermals? On Idle the card is around 60-66C and then on load the card runs around 77-83C. This is on the default fan curve and with a more aggressive on I can get it at 77C at around 90% fan speed at load. 
 
Below is a pic of my current fan setup. There is a missing fan because I am waiting for my new corsair fan to come in. When I did the testing I had all corsair fans and one fan that came with the Lian Li case where the missing fan would be. All fans are 120m
 

My XC3 Ultra also ran hot into the 72C-74C range on an O11D-XL stock full of fans including 3 blowing cool 22C ambient air from the bottom directly into the card. XC3s run hot. When disassembled the card to install the hybrid kit, I noticed one of the thermal pads for the power delivery was not making as strong contact as it should, and the thermal paste on the GPU was already pretty dried up. If you feel comfortable with disassembly, you could try repasting the card with good quality paste like Kryonaut. Also get better thermal pads, the included thermal pads are one use only. You could loose a few degrees going this route.  It will not void the warranty and you can use the instructions from the hybrid kit installation PDF to disassemble the card safely. 
 
You could also consider buying the hybrid kit. My temps lowered significantly with the card running in the 55C range now and with a modest +125 on the core it boosts very close or stays at 2100mhz most of the time. You definitely have the radiator space on the front of the case.  

How are the new temps after repasting/replacing thermalpads?

avex102

selarom

RoyalMuffin
Recently just scored a 3080 XC3 Ultra from microcenter and despite being a beast in gaming should I worry about its thermals? On Idle the card is around 60-66C and then on load the card runs around 77-83C. This is on the default fan curve and with a more aggressive on I can get it at 77C at around 90% fan speed at load. 
 
Below is a pic of my current fan setup. There is a missing fan because I am waiting for my new corsair fan to come in. When I did the testing I had all corsair fans and one fan that came with the Lian Li case where the missing fan would be. All fans are 120m
 

My XC3 Ultra also ran hot into the 72C-74C range on an O11D-XL stock full of fans including 3 blowing cool 22C ambient air from the bottom directly into the card. XC3s run hot. When disassembled the card to install the hybrid kit, I noticed one of the thermal pads for the power delivery was not making as strong contact as it should, and the thermal paste on the GPU was already pretty dried up. If you feel comfortable with disassembly, you could try repasting the card with good quality paste like Kryonaut. Also get better thermal pads, the included thermal pads are one use only. You could loose a few degrees going this route.  It will not void the warranty and you can use the instructions from the hybrid kit installation PDF to disassemble the card safely. 
 
You could also consider buying the hybrid kit. My temps lowered significantly with the card running in the 55C range now and with a modest +125 on the core it boosts very close or stays at 2100mhz most of the time. You definitely have the radiator space on the front of the case.  

How are the new temps after repasting/replacing thermalpads?

The Temperature came way down with the new hybrid kit, which in turn gave me higher sustained clocks. It felt like an upgrade. I didn't really test new pads and repaste before installing the hybrid kit though if that's what you are referring to. I am waiting on new thermal pads and some adapters to open up the card again, install the pads and use 4-pwm adapters to power the fans from an outside hub instead of from the card pins and replace the fans with ARCTIC P12s in push/pull. The P12s are better optimized for radiators. With the adapters, I can still run the fan's pwm signal from the board, but not the power to drive them. The same for the pump as well. My hope is that by not using power from the board to power the fans and pump, I can outsource that power so the board has that power available to use it on the GPU and memory. We'll see

Topic is bit old but will give a try;

Got 3080 XC3 without back plate. Had to do thermal pads because previous owner did thermal paste everywhere and it was nasty job since he spread thermal paste everywhere so i was like let's do proper job. First time i did 1,2,3mm pads according to youtube video and temps were high. Soon as i start warzone it goes so fast up to 80-82 and i didn't keep playing for so long. 
Also since i am running big tower cooler on CPU i was thinking going AIO because i feel that head is being transferred from CPU cooler to GPU.

Ordered Kritical pads, all custom cut. Did them yesterday and got bit better temps. What happened suddenly; PC crashed and couldn't boot. It kept restarting and couldn't boot. Also red lights on GPU where connectors are were flashing. Even with different 3080 that i had on hand (have to do pads there since got them from same guy) couldn't boot.

Removed GPU and finally PC somehow boot. Today will keep testing it but i am suspicious about PSU. All parts are new, besides GPU.
12700K
Z690
16GB DDR4
850w Evga Supernova 
3080XC3 EVGA
Case NZXT H5 Flow, 2 fans intake, rear exhaust so it's open case in front and top as well.

Any advice, suggestion or opinion would be appreciated.