Overheating CPU in idle

[Wethouse_noobmeister]

Hello, hope you can help a pc noob 😀
I have a problem with my intel i5-4670k, I normally run temps between 35-45 degrees celsius, but like 2 days ago when i started the pc it went up to 60-70 degrees and this is while i only have a browser tab open. So i decided to browse around looking for what could be wrong, and then all of a sudden it dropd back down to 40... i tried not to shutdown my pc and just make it go to slumber and when i started it up the next day, no problems, but last night i shut it down and when i started it today, it went back to the idle 65-70 temps... im abit confused and ive tried to clean it for dust( tho without taking any parts off) but it doesnt seem to work, my question is can this be software related or bios. I have very little knowledge when it comes to this stuff, so i hope you can help me, FYI my CPU is watercooled by a coolermaster, no clue what the name is, didnt build it myself.

 

[NerdyComputerGuy]

change themal paste

 

[scout_03]

check if the pump stil work and tight on the cpu then check the fan on cooler if it spin since you dust it off you may have unplug one of those and temp will rise .

 

[Wethouse_noobmeister]

I guess i have tried anything that didnt envole taking any of the parts off, i tried tightening the cooler on the CPU all fans are spinning and they all go on max speed right as i turn on the pc, guess its time for me to buy some thermal paste, tho ive never build a pc, so hope i wont break anything, thank you for your answers.