GPU's have built in thermal protection to turn the card off if it gets too hot to prevent damage. Sounds like the card just died for some other reason. You can still rma it.

That's correct, I am using PETG. I've already started putting together a new loop but wanted to see if I was going to have to plan around a potentially different video card before I finished that up.
I actually do have a fluid temp sensor, I really don't know how I could've missed temps going up super high. As far as the overheating, as soon as I can get my system back up and running that's my #1 priority, but currently without the GPU which was a significant source of the generated heat I'm a bit  stumped. When I first built the system in November I had some issues with the BIOS recognizing the pump header especially after a wake when which is why I put that as a possibility for the starting cause, but that hasn't happened since I resolved the initial issue.
Thanks for the advice!
 
ETA: I didn't know about the 40C thing, though. I don't think my fluid generally gets that high, but what I'd read was that PETG starts to become malleable around 60C, so I really only paid attention to keeping it below that. In any event I'll be doing what I can to lower temps in general even aside from whatever is causing the current overheating issue, but I will definitely be keeping that new number in mind for those improvements.

GTXJackBauer
PETG won't show signs until the 60c area just like soft tubing which is around 65c which by than the tubings are compromised.  40c is fine.  Sounds like you hit VERY high water temps to see the hard tubing compromised which says something went wrong with your loop which needs to be investigated and monitored at all times till the issue is fixed and for future reference, you'll want to add some type of alarms along with water temps. 

List of your loop including pumps, fans, rads, blocks, etc. and some images would help.
 
Not to overcomplicate things for ya but if you're up for the challenge, you could use something like this instead of MB headers and run the alarms in a software, etc.

Yeah about that... according to EKWB 40C, they even have it posted on there site. Talked with EKJake and got confirmation on that as well. 

The loop is the video card mentioned, an i9 9900k, and a 360 thick rad from EK (XE series I think?) all in a PC-O11 Dynamic case with the distro block built for the case. Order is pump (in the distro block) to GPU, back to distro, CPU, back to distro, then rad. All EK blocks, tubing, and fittings other than the distro plate made by bitspower, and the block on the card is EVGA obviously. I know the single 360 rad is pushing it for the hardware it's cooling, but my temps have always been low, I'm not overclocking or pushing my computer much at all at the moment, and the airflow is good. The plan is to redo the loop once I can figure out how to fit another rad in there, but with the way my temps have been outside of this specific instance (this computer has gotten a lot of use in the 3 months I've had it running), I haven't wanted to make a bunch of major modifications until the weather warms up (midwest ambient temps are pretty low this time of year). Fluid is EK coolant, no coloring.
 
I added a picture that I believe was taken right after leak testing was finished and I booted it up for the first time.

jasoncodispoti
Assuming that you are using PETG, in a well built loop 10/12mm tubes will start to deform and droop at fluid temps as low as 40C. If the tubes are sagging you need to find the source of the overheating issue. Also I would recommend replacing all of the tubes... you blow a tube when the loop is running and chances are you will lose everything in the case depending on where the tube is at. As far as the GPU being toast... I guess anything is possible, but thermal protection in theory should have prevented damage to the GPU. You can always try an RMA the card however if it is less than 30 days old and purchased in the US I would suggest returning the card and purchasing a new one.
 
Top Tip: 
Do not build a liquid cooled loop without a temp sensor in the fluid with some type of active monitoring in place. 

 
Damn.  If I ever build a custom loop I'm going to use automotive coolant hoses, assuming I can get proper fittings.  Having a pile of wimpy plastic tubes holding back fluid from several thousand dollars of electronics sounds like a bad idea, lol.

GTXJackBauer
That's crazy if EK says their tubing is 40c.  A general google search will state 62c but I guess EK's tubing isn't as strong. Some of us will hit 40c water temps in the summer days with AC on or at least with more than 1 GPU.  I used to hit 42c on dual 780s for a long time with no issue since I used soft tubing.  Still using the same tubing as we speak.

Pretty much all of the 10/12mm PETG tubes will start to deform at 40C depending on usage... its mostly due to how thin the tube is. If you step up to 12/16mm this becomes less of an issue... You generally want the coolant temp to be within 10C of ambient air temperature so about the max you would want the room to be would be 85F which would be 29.4C so fluid temp should not be more than 39.4C in those conditions. 

I just went back to look at my Reddit conversation with EKJake about this, looks like I misstated the temperature above. 
 
"...The short answer is that PETG sees deformation at around 60C coolant temps. But it's possible that lower temps, say 50C+, can lead to deformation over time versus more rapid failure..."
EKJake. 
 
What lead to this conversation with EKJake was the following; 
If you go to https://www.ekwb.com/shop/ek-hd-petg-insert-10-12mm-10pcs they sell PETG Inserts where EK states the following...
"The EK-HD PETG Inserts are EK's way of battling against potential deformation hazards that the use of PETG tubes present. PETG tubes are extremely popular because of the ease of use and their flexibility. On the other hand, PETG tubing, especially the thin tube wall models (10/12) are prone to deformation when exposed to high temperatures (40°C and above). The deformation rate depends on the duration and maximum temperature reached. These temperatures can be reached with pump failures, water block clogging, etc."
 
Too me this implies that the PETG tubes are deforming around 40C, but EKJake seemed to contradict that statement. From personal experience I can tell you that I have ran into issues at 40C. I have a single tube that travels up the side of my case from the very bottom to the very top and one day I did have an issue that allowed the fluid to reach near 40C, but not exceed it and that longer tube did bend. As a result I had to drain the entire loop and replace that tube that had started to flex. Now in this situation I believe that it was less about the temperature of the fluid and more about the length of the tube. However it only happened when the fluid temps reached near 40C. 
 
If I had known about this issue with 10/12 tubing prior to building my PC and purchasing fittings I would have gone with the thicker tubing, but at the time EKWB did not have this information posted on there site.
 

It's possible EKJake is calling out 40c as a means to have people aim for lower temps to give a greater safety threshold. Why play with fire by being ok with having temps so close to that danger zone? Ya know?

While although you call out you're not oc'ing your 9900k, even stock that chip pumps out some heat. I personally would have more Rad for a 9900k and 2080ti in the same loop. But that's coming from someone who's always believes in extra radiator space just to be safe, aka self admitting overkill.

I may have missed it in your posts, but do you have any temp benchmarks with the tried and true tests? Prime95, Heaven Benchmark, 3DMark, etc? If I were you, along with swapping out your tubing I'd check your cpu thermal paste application as well. Might as well use the time while waiting for you rma to do an overall sanity check.

You get something like this and then you can see if the fluid is moving or not.. no flow the pump is not running.

https://www.microcenter.c...hexagon-flow-indicator

I use 2 of these.. 1 for ea pump.. could of just used one. I used them for function and to help with a major bend in my hardline.

captainm
That definitely could be helpful for a major bend - that isn't something that I'd thought of before. However, I have an easy enough time determining if the pump is running or not if I look for it, it's more that if I don't specifically look for it I won't know that it isn't running. Unless these flow indicators make a lot of noise (which would defeat a lot of the purpose of my build as I like how quietly it runs), I feel like it wouldn't really help my specific problem as I would still need to specifically look at the indicator to see if it is spinning. That is a helpful idea, though. Thank you

 
There are a few flow meters with displays on them, giving you live readings if you're interested.
 
Koolance INS-FM18D

 
 
Thermaltake Pacific TF1