The temperature of my CPU is weird after adding a case fan

[padtestabc]

My pc has two exhaust case fan (top and rear) with 8600k. The temperature of the CPU is 84 C maximum in prime95 stress test. I was not happy with this temperature so I installed an extra fan (intake) at the front. I ran the stress test again and the maximum temperature increased to 88 C. It is not make sense.

For more details, the original fans are connected to the psu by one cable while the third fan is connected to psu by another cable. Is it possible that the fans would spin slower which affect the cooling performance? If not, what is the reason? And how can I fix it?

cpu: i5-8600k oc to4.4Ghz
gpu: Asus rog strix 1070ti
cpu fan: cryorig h7
ram: G.skill aegis 2x8GB 3000Mhz
Mobo: Asus rog strix z370g
Case: Nzxt S340 elite
Psu: Antec Neo eco 650 gold

 

[gingerrankin]

Make sure that the measurements have been made with the same ambient temperature.

You can do the test with the case open and you will know as much as you can get with the case fans.

What most influences is the CPU cooler. Make sure the fan pushes fresh air into the processor (and does not absorb it). If you have moved the CPU cooler you must change the thermal paste.

 

[madmatt30]

Are you sure the front fan you installed is the correct way around ??
Because with a temp increase it looks to me that you may have actually fitted it as an exhaust too.

On another point I've never understand why the s340 comes with 2 fans but both fitted as exhausts.