suddenly hot GPUs - total mystery

[Safetytrousers]

Msi x470 Gaming Plus Max - Ryzen 3600x
4 fan rad + 2 fan rad - loop running well

Ran with waterblocked RX 5700 for months without issue, always mining while using net etc. Temperatures nice. Then with waterblocked 2080ti without issues.
I got a waterblocked 3090 (working fine in other PC). I put it in slot 2 with the 5700 in slot 1. Providing PCIe side connector power with a 500w PSU. But it didn't work well, gradually fading in Hz then failing to be detected. I put it down to the EVGA G2 750w supply not being able to manage the extra 75w PCIe slot power. So I put a EVGA G5 1000w supply in, 5700 ran fine the first day it was in.
Next day I moved the 3090 to my other PC with supplementary power from the G2 (works lovely).
I put 5700 top slot in the MSI and 2080ti second slot (8x8). The 5700 was fine but the 2080ti had become super hot and thermal throttled. I put it down to something dislodged in the block so I redid it (although nothing seemed amiss) and repasted it, or a conflict.
I then put the 2080ti top slot on its own (in loop) and it was still super hot after trying several things. I took it out and put the 5700 in top slot on its own. It too was and is now super hot. I have tried everything I can think of software and BIOS.
What is going on?
Screenshot desktop idle after a couple of hours on:

 

[StephenJ]

Have you checked if your pump is running fine, and does your cpu get hot at all ?

 

[Geckovich]

Loop not sufficient to cool both cards? Cards plumbed in parallel with different block flow rates causing issues?

 

[wookiee87]

could be a motherboard problem as you've said 2 cards have been affected, i'd have a look at the board for anything around the pci e slot that looks a miss, plus take out the 2 cards that are miss behaving and check the gold pci connectors at the bottom of the cards, look for any discoloration or anything really that looks out of place, if you find nothing go back to your x470 mobo and look at the whole board for anything that may look out of place, bulging caps etc, if you find anything post a pic and possibly brace for a replacment component (mobo) maybe.

you could download hwinfo64 and check the sensors to see if it's a problem with already installed software on your pc, outdated versions will report incorrect values, with hwinfo64 you can look at the psu too and if any value's are flagged in red, you'll be able to narrow down the problem.

if the above dosnt shead light on the problem, then i'm not sure what it could be, you coud try the 2 affected cards in the pc that has the 3090 in in, if the 2 hot cards work then something is wrong with the x470 setup you have.

 

[TrojanWhore]

From your screenshot/temps the only thing that I could think would be a flow rate issue, either a blockage/kink or as geckovich suggested, a parallel loop bypassing the gpu blocks.

What's your loop order and what pump?

Also from the screenshot it appears there was SOME gpu load for the first ~30% of the time the graph covers, with an associated (slight) drop in temperature after that. Any idea what was causing that load?

 

[Safetytrousers]

The load would have been watching a YouTube video.
The loop was flowing fine when I was refilling it several times trying to make the 2080ti behave. It is a DDC pump at max speed.
All the tubes solid also indicate the flow is good.
Order is pump to GPU, to EK XE 480 on top of case (on its side) into EK two fan job rad back into reservoir. This all worked fine when I first set it up. Tubes feel cooler than my main PC with 2 3090s mining, but the GPUs running cool. The air coming through the top rad feels cool.
The readings in HwInfo agree with GPUz. The loop currently just has the 5700 in it, which was running fine mining while internetting for ages with just the 2 fan rad and the G2 750w.

I could try the 2080ti in the main PC. I've spent my last money on a x570 Tai Chi and a Strix 850w. I'm returning the G5. (the Main PC has an 850w PSU with one 3090 connected to the G2 750w, the main PSU reads 735w from the wall)

 

[Safetytrousers]

SOLVED

Because I was running out of tubing I was going and coming out the same side of the blocks. Simply changing it to opposite sides has solved the situation. £££
I've never read or seen in the countless YT videos I've watched not to do same side. EK instructions don't say about it either.

 

[StephenJ]

Sounds odd as i don't see what would change, but fixed is fixed

 

[TrojanWhore]

SOLVED

Because I was running out of tubing I was going and coming out the same side of the blocks. Simply changing it to opposite sides has solved the situation. £££
I've never read or seen in the countless YT videos I've watched not to do same side. EK instructions don't say about it either.

Came back to ask this - so you were essentially bypassing the gpu block?

Glad you found it the issue