i5-2400: good idle temps, very high prime95 temps

I've recently switched cases to a Fractal Define R4 (windowed).
My GPU temps are fine (~70C after 15 minutes of Furmark testing).
However, I'm having problems with my CPU temps. It is an i5-2400 (no-k) without any overclock and is using the original Intel heatsink and fan.

I switched motherboards as well so I had to scrape off the original thermal paste and applied Artic Silver 5. This was before I switched cases (had a Rosewill Challenger). I didn't run prime95 in the old case but did some gaming (ME 2, Arma 3, SWTOR, FIFA 14) and didn't have any issues.

Idle temps are currently 35-37C on all four cores. This is lower than they were with the original thermal paste (~40-42C). But they hit almost 80C within 2-3 minutes of starting a prime95 test.

I would think I applied the paste wrong since it was my first time except that the idle temps are as low as expected. The case currently has the two stock fans, with one mounted upper front intake and the other as rear exhaust. They are both attached to the cases fan controller and running at 12v.

The CPU fan alternates between displaying 0 RPM and ~2100 RPM as reported by speedfan, HWINFO, and ASRock Extreme Tuning Utility. However, visual inspection revealed that it is spinning even when software says it isn't.
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More about 2400 good idle temps high prime95 temps
  1. How did you apply the paste? More (better) fans and a better cooler should help immensely.
  2. ewok93 said:
    How did you apply the paste? More (better) fans and a better cooler should help immensely.

    I applied the thermal paste using the vertical line method suggested by the manufacturer. I also tinted the heatsink as they suggest.

    I've ordered two more of the stock case fans as they are on sale at Newegg and I'm not a man of infinite resources. I tested my system when I initially built it (late summer '12) and the load temperatures were fine then. I don't remember exactly but they were close to 65C. Is it possible that the cpu fan is failing?

    What heatsink would you suggest? Quiet is more important than extremely cool since it's not a K series. That said it might be nice to be able to upgrade to a i7 K series later and use the same heatsink.
  3. Hyper 212 Evo would be good choice if you plan to upgrade to a K series later.
  4. It's great even if you don't want to. It's compatible with just about everything and is a really nice cooler, and will run anything nice and cool.
  5. How quiet is the 212 Evo compare to the stock HS? Would you recommend replacing it's fan with something else?
  6. Best answer
    It's much quieter. I'd keep the fan that comes with it.
  7. ewok93 said:
    It's much quieter. I'd keep the fan that comes with it.

    Great. Thanks for the help.
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