I'm running a 2080TI Founders Edition.  Same problem here as well, but I have definitely fixed it.  If one or both fans suddenly go to max rpm it is because the card has a sensor reading of 105c or greater.  For me the fix was to take the back-plate off, then remove the heat-sink assembly, apply new thermal paste to the GPU, and replace the thermal pads as required.  All can be ordered from Amazon.  Card works fine now.
 
Forgot I already posted about this.....sucks getting old.  Consider this an update, its still working just fine!

Even if that is the solution....no way in hell I could figure that out as you need the exact dimensions for all the pads used and that might require me not only to purchase several different mm varieties but also then measure out the correct length and width for each piece. Took it to a mom and pop computer shop....nobody obviously suggested that (probably way too much work and risk) I have the gigabyte aorous version of 2080ti but the issue is exactly the same....

dsbello
I've had this card (EVGA GeForce RTX 2080 XC ULTRA GAMING) about a year now (purchase date 11/2018) and this last week it started this problem. Once it hit 80°C the fans would shoot to 3000RPM then at 79C it'll go back to normal. Opened it up and reapplied thermal paste and it's better than new! Thanks!!
 

way too much TIM, need only 1/50 as much, meant to be thin not some blanket