Ok. That sounds an awful lot like either your pc is running very cool, or what you are seeing is liquid temps, not cpu temps, which is very hot.
The krakens can report either, depends which setting its on in Cam. If it IS liquid temps, 42°C is quite hot, consequently the fans will be trying for a much lower temp on the curve, so will spin at max speeds or close. On my x61 cpu temps gaming will be closer to 55°C but liquid temps get to @35°C at most. At 42°C liquid, expect the cpu to be running closer to 70-80°C. How the temps are read makes a huge difference, liquid temp is default on, not cpu. If this is true, it would fully explain why your fans are so fast, even on silent mode.
Which really makes me wonder why your cpu is so hot. Even at a 4.9GHz OC on my i7-3770K under torture test, liquid only got to 36°C after ½ hour test and cpu hit 72°C