H100iGTX not cooling properly, or is my CPU too hot?

[J-5]

Trying to figure out if I have a problem with my liquid cooling pump (H100iGTX).  CPU has been running up to 90C for a few months.  Figured the thermal paste was just getting old so I replaced it this morning with a non-electrically conductive thermal paste (AC-MX4).  I did remove the old paste, using isopropyl alcohol to fully get rid of the old stuff.    Now when I try to do something CPU intensive the CPU temp goes up to 100C and I have to shut it down and wait for it to cool.  Add to that the air conditioner in the apartment has gone out.  GPU seems fine even in the warmer apartment (Temp #1 45C, Temp#2 60C).  

At no load (5% CPU usage) using  iCUE: Coolant Temp: 55C, Pump 3150 RPM, CPU (i7-5930K): 75C, CPU Fans: 2750RPM.  I did set the pump to "Extreme", which seems to keep the temperature from slowly climbing.

Does that seem like reasonable coolant temperature?  I at first thought the pump wasn't functioning well since the liquid conduit leaving the pump was warm to the touch close to the pump but was not very warm as it approached the radiator.

At this point I'm having trouble figuring out if the problem is if the CPU is running too hot for no reason or if the cooling system isn't working well, causing the CPU temps to climb.  Any ideas how to figure out what the problem is?

[LeDoyen]

55°C coolant temp at idle, it seems either you stuck the radiator right against a clogged filter pushed against glass and sealed with gorilla tape, or your AIO cold plate is clogged and you have little to no water flow inside.

Normal temperatures for idle would be roughly 5-7°C above ambient.

If blasting the fans manages to stop the temperature from climbing further, i lean towards an almost complete clogging of the cold plate.

How old is this AIO?

Edited May 13, 2022 by LeDoyen

[J-5]

7 minutes ago, LeDoyen said:

How old is this AIO?

Just about 7 years old.  Maybe time for a new one?

[c-attack]

Yes, time for a new one. 7 years is a very good run for the GTX/v2 series AIOs, but this generally how it ends. The coolant can’t get around at the necessary rate as restriction points have built up over the years. The 55C liquid temp and “have to wait for it to cool down” are classic indicators. Neither of those conditions will happen with poor cpu/TIM/block contact that produce high cpu temp but low liquid temp. 

[J-5]

Thanks for the advice.  Browsing the internet was not getting me that specific information.  Replaced the cooler and it is working great now.  Didn't want to spring for a new one if that wasn't the problem.  Appreciate the expertise.