At the WD web site, the temperature listed for MBWE as
Operating 5° C to 35° C
Non-operating -20° C to 65° C
The original one (500G MBWE II) was running around 50 to 55 C. I added a USB fan, the temperature at running ranges from 36 to 41. as you see, it is much better the original fan, but still a bit out of the listed temperature range. It seems ok. Can you list your temperature here, so we can see a clear picture how are the temperatures?