X51 R?, need to replace heatsink

https://www.amazon.com/s?k=dell+WKGR1%2C+7C20C&i=electronics&ref=nb_sb_noss

Dell sometimes has fan wires swap things around.

Replacing just the fan will work with NON DELL FAN unless you make sure the wires go to the right places.  Some dells use standard wiring.

https://www.amazon.com/Pocaton-Female-Socket-Connector-Cooling/dp/B073XJV5L9

https://www.ebay.com/c/1785079697

Delta AFC0812DD
Dell PN 7C20C-A00
Fan 80mm * 80mm * 20mm 12v 0.75a 4pin

Dell swaps the wires around so that you will fry a dell fan on standard and the other way round.

It has 5 pins but only 4 wires are used.

Dell does not publish this.

I believe this is correct.

YMMV

4pin PWM on 3 pin

DELL FAN WIRES AND COLORS

The casing for my original X51 R2 cooler got brittle over time and shattered. Cannot find anywhere to purchase. The following is what worked for me.

Purchased the following cooler from Newegg. 

https://www.newegg.com/p/2RM-000M-00ER6

for $20. It fits perfectly in my Dell X51 R2. It is taller than the original, but can still work if you cut the shroud which I will explain below.

Replace the fan on the above with your original since the original is shorter in height. This will come in handy as it will give more space to fit the cut shroud.

New heatsink plus original fan.
Above is system with heatsink from Newegg plus the original fan. Make sure the fan pulls air away from the heatsink and not pushes it. If pushing, then simply turn around fan so it pulls air away from the heatsink.

Closeup of heatsink and fan.Above is a closeup of the new heatsink purchased form Newegg plus original fan 

Cut approximately 1/3 of shroud. Shown here with another original for height comparison
Above I cut off 1/3 of the shroud (used a hacksaw blade), then smooth the edges with sandpaper (could use a file) so they are all flat. Important - Only cut three sides. Do not cut the slanted side that goes against the perforated chassis. In photo I've placed it next to an original shroud to compare the height.

Modded Shroud installed.
Finally I installed the cut shroud. As you can see, there is still lots of space for the air to flow out the system. Initially, the side panel did not fit so I took off the shroud and filed it again and tried until I could close the side panel without forcing it.

I've been running the system like this for a few months and it works perfectly. I normally run my X51 in an air-conditioned room and the temp is usually 33 degrees Celsius for normal computing and stress testing with CPU-Z carries it to around 69 to 71 if left for a while.

System is Alienware X51- R2, 16GB RAM, 330Watt Power Supply. GTX 1050Ti GPU, and 2 x 1TB Samsung EVO SSD drives.