lijeu,
On behalf of Tom's Moderator Team, welcome aboard!
Although you can use your IR thermometer to measure the temperatures of the VRM's, contrary to
anotherdrew's suggestion it's pointless to attempt an external IR temperature measurement of the processor. Here's why:
Sensing thermal performance by touch is like feeling a campfire from 3
meters. Since hundreds of millions of
nanometer scale transistors are densely packaged into a tiny Die, heat dissipates over relatively large areas and thermal gradients to the cooler, about 3
millimeters from the Cores. (3 millimeters = 3,000,000 nanometers).
Although some heat dissipates to the substrate, socket and motherboard, most heat dissipates to the cooler through several thermal gradients; Cores > Die > internal TIM (or solder) > IHS > external TIM > cooler. Even at 100% workload nothing will feel hot; exhaust airflow, cooling fins, heat pipes, radiator or water block will feel warm, and liquid cooling tubes will have a minimal temperature differential.
To verify the Core temperatures you're seeing in HWMonitor, please download and run HWiNFO -
https://www.hwinfo.com/download.php
HWiNFO is known to be a very accurate and reliable monitoring utility. Select "Sensors Only" when you start HWiNFO, then compare "Core" temperatures with HWMonitor. If they agree, then as
anotherdrew mentioned, your 8700K has a bad Digital Thermal Sensor for that particular Core. In such an instance I recommend that you RMA that processor, as you can expect to have problems with irregular operation due to false thermal throttling.
Also, Tom's has a Guide you should read:
Intel Temperature Guide -
http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html
Once again, welcome aboard!
CT