Had a great deal of trouble with FanExpert2 and the Corsair 3-pin fans the AF120 and SP120. Works better with 4-pin fans, not sure why, PWM information or interface maybe, could be the extremely low current that they draw from the motherboard.
Make sure you save-to-profile in FanExpert2, its easy to miss that step and move to another fan, I messed it up a zillion times at first. So started saving each fan to the same profile, before moving to the next fan.
RealTemp, Techpowerup Open Hardware Monitor 4.0, and AI Suite 2 all show the same temps, CPUID HWMonitor seems to add 10C to every reading.
Here are some idle temps in Techpowerup Open Hardware Monitor 4.0:

AI Suite 2 says idle CPU speed is 1600Mhz with Intel Speed Step enabled, this software says 1400Mhz, otherwise the temps are similar.
Is your CPU temp of 48C idle or load? That should drop lower if you enable Speed Step in the bios, so the CPU throttles down when you are not using the 4.2Ghz overclock or whatever o/c you have set up.
Also try one of these other hardware monitors, your temps might read lower, not sure why CPUID reads so high, but if 3 out of 4 hardware monitors read the same I would throw out the one that doesn't, but then I like my O/C served cold.
😛
Maximus Obsidious “Max”
Chassis : CaseLabs M8
PSU : Corsair Platinum AX860 (Seasonic) w/Corsair Gen2 AX Cables
CPU : Intel 3770k 4.2GHz Vcore 1.282 Delta T=2.5C at idle
RAM : Corsair Dominator GT 2133Mhz 2X4GB kit
Mobo : Asus Maximus V Extreme (you and me baby)
GPU : Asus 6870 DirectCU (Asus GTX780 5GB Coming Soon) 😛
Cooling : H100i Sanyo-Denki San Ace 120(x6)
Internal SSDs : Intel 520 120GB(x2) RAID0