I'm building an i5 system for a course of mine, and this is my first time actually building a system (though I have lots of experience inside PCs). The other day I fired it up for the first time, and while I was messing around in the BIOS I found the page that displays the hardware temperatures and it said the CPU core temp was a whopping 98C. It was only running for a minute or two. Immediately I shut it down and opened up the case, to find that one of the pins on the stock Intel cooler was a little loose. Checking the back of the mobo, the two pins on the bottom were in fine but the two top ones were not. I was able to tighten the two top pins without having to reseat the cooler, but the black middle pins aren't as deep as the bottom ones. I restarted the computer and running for 10 to 15 minutes the BIOS reported the temperature to be around 55C- better, but still seems a little hot to me. I have an i5 2300.
TL;DR: Messed up installing the stock Intel cooler, fixed it and it lowered the temps to 55C. Should I take the cooler off completely and re-mount it? Would I need to put new thermal paste on? The computer itself has only been running for 20 minutes at most and that was in the BIOS only. No OS installed yet.
Your best option is to take off the cooler, clean it and the CPU off and reapply the thermal paste to get optimal performance out of the stock cooler. Do keep in mind that the CPU will run a bit hotter in the BIOS, especially if you stay in the BIOS for a while, as the CPU cannot idle until the computer boots into Windows.
Yes I would agree. Plus when you take off the cooler you can see how a good a spread you got and maybe choose a different method if it wasn't good coverage. Remember you dont want alot of compound but it does need to spread pretty good.