same problem
cpu : i7 4790k
m/b: msi Z97 gaming 5
case: coolermaster haf x fans 3x200mm(2 top intake/exhaust+1side intake) 1x230mm(front intake) 1x140mm(back exhaust) 2x120mm for gpu/ram inside
cpu cooler:noctua NH-D15
the cpu run stock speed/volts/mhz
room temp: 28c /cpu temp idle 30c /mb temp 34c
with MSI(R) Intel(R) Extreme Tuning Utility stress test in half sec 70c+ when finish in half sec 34-36c
thermal paste check twice after tests
fans speed 50% 75% 100% almost the same temps +-3c