Question Custom Water loop temps

RJamesRJ

Prominent
Aug 1, 2019
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I recently just re-worked my custom water cooling loop. I am curious as to why my CPU temp reads 10-12°C higher then GPU. To get some context of the loop. It splits coming out of the pump and goes to the CPU and GPU on their own line. (I have had it like this for years now with no major temp differences.) Then coming out of the CPU it combines back with the out side of the GPU.(Which is the newer portion, essentially using it as a Tee) after that is goes to the cooler, then back to the res/pump. My assumption is the water being pushed out of the GPU is causing the water coming from the CPU to be slowed. Which in turn makes that whole line slower allowing the heat to sit in the water block. However, it wasn't always like that. When I first changed it they use to sit within 1-2°C of each other and slowly climb together. So, I'm not quite sure if my theory is right because this issue would have been there sense the beginning. But I can't think of another reason as to why it is different now. I am also only getting these reading through monitoring software(Haven't looked into physical reading sensors). Which with the ones I have looked at come back with the same results. It isn't a big issue because my temps are still lower then any concerning temps. Just curious if anyone has any other ideas.
 
I recently just re-worked my custom water cooling loop. I am curious as to why my CPU temp reads 10-12°C higher then GPU. To get some context of the loop. It splits coming out of the pump and goes to the CPU and GPU on their own line. (I have had it like this for years now with no major temp differences.) Then coming out of the CPU it combines back with the out side of the GPU.(Which is the newer portion, essentially using it as a Tee) after that is goes to the cooler, then back to the res/pump. My assumption is the water being pushed out of the GPU is causing the water coming from the CPU to be slowed. Which in turn makes that whole line slower allowing the heat to sit in the water block. However, it wasn't always like that. When I first changed it they use to sit within 1-2°C of each other and slowly climb together. So, I'm not quite sure if my theory is right because this issue would have been there sense the beginning. But I can't think of another reason as to why it is different now. I am also only getting these reading through monitoring software(Haven't looked into physical reading sensors). Which with the ones I have looked at come back with the same results. It isn't a big issue because my temps are still lower then any concerning temps. Just curious if anyone has any other ideas.
What are your CPU and GPU
 

RJamesRJ

Prominent
Aug 1, 2019
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510
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I wouldn’t be concerned. Newer CPUs run pretty warm and a 2070 is in the cooler side. I have a 5800x and a 3070 and I have a 8-10C difference with my CPU being higher. I’m running a 480 and 360 rad.
Yeah! I'm not concerned about it. As I said my temps aren't getting high enough to be concerning. Was just trying to understand why it would be like that if they are part of the same system.
 

rubix_1011

Contributing Writer
Moderator
Your parallel loop setup is very similar to how I have mine: 9700k and RTX 2080 on EK blocks.

I split a Y-fitting out of my pump and run inlet to each CPU and GPU, then close the Y-fitting on the back side of each, which runs into my pair of 240 PE radiators, then back to the D5 pump/res combo.

For starters, your CPU and GPU operate differently, so they won't be 'the same' at all times. Your CPU uses a substrate compound between the CPU core dies and the integrated heat spreader (where you apply paste) while a GPU block makes direct contact with the GPU die itself. This is more efficient for cooling, but in turn, your GPU is also rated at a higher TDP, meaning it will pull more power and output more heat. So, it is a trade off.

However, if the CPU and GPU are exactly the same as they were before, my guess would be the reduction in flow would cause the difference. As you split a coolant line, you are effectively halving the flow rate and head pressure between the 2 sections of the Y-fitting. With a serial configuration (all items in order, one after another), you have full flow and head pressure between all, so it is possible that the dip in flow and pressure to your CPU block might be what you are seeing. To counter this in my loop, I pulled my EK Classic Supremacy CPU block apart and removed the jet plate directional pieces and allowed the block to be as free-flowing as possible. This made flow rates in my entire loop improve. Higher flow usually means better cooling performance. I made the choice to do away with the CPU block restrictions as a trade-off for what would normally be OK for a higher pressure flow leg of the loop and made it optimized for lower pressure, lower flow to allow it to flow faster overall.
 

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