A51 R2  it is oem AIO made by Asetek for Dell.  according to Cass  Original alien cooler (K31VH) for R2 is entry-level 27mm wide (120x27) which is also used in R4/R5 R4/R5 also uses a newer AIO which is backward c/w R2. R2 = K31VH or H4TYR (slightly older gen Asetek 27mm circa 2014) R4/R5 = NVDDX (newer gen Asetek 27mm circa 2017) I would use this opportunity that original AIO died to upgrade the cooler if within Dell oem family rather than keep on using the same used old stock. The newer pump uses sleeved tubes which look more premium than the plain tubes of old pump. [IMAGE][IMAGE]  
I purchased my Alienware Area-51 R2 around September of 2015. I know, it's an old PC, but it still has some decent components, the PC has a GTX 970, intel core i7-5820k 32gb of ram The PC ran like a beast up until 2021 where I can remember clearly the PC running perfectly fine until I played the game Anthem, upon loading the game the PC fans kicked up to 100% I never heard my fans get this loud where it sounded like a Jet Engine for a good minute or so, until I closed the game application. Since then, my CPU has not been the same since.  on a PC where the fans were barely noticeable, now are running at 60-70% usage to keep the CPU from reaching even higher temps, the CPU now just booting up will reach 70C, and on Windows reach up to 90C - 92C the PC is basically unusable now. I did attempt to see if the Thermal paste dried out, so I redid the thermals, it helped a little lowering the temps to around 85C - 89C, I also tried reseating the CPU just to make sure nothing got moved around weird, but the temps remain pretty much the same. I did notice some noise from the AIO pump, I hear a rattling noise upon booting up the PC, so I don't know if my AIO Pump died? I also notice when the CPU gets up to 90C that one of the hose's gets extremely hot where you can burn your hand just touching the hose, while the other hose feels like room temperature to the touch. I was questioning if I should try to go on Ebay to buy another AIO pump, or is there damage to the CPU that I would need to replace the CPU instead? Anyone have an ideas what could be the issue?
Area-51 R2, CPU reaching 85-90°C on Windows Desktop