computer turns off suddenly

hello, i have installed 2 case fans to have to air flow. and when i booted the pc couple of mins later, it suddenly turns off. i unplug both of the case fans and did the same thing.
thanks

It does sound like a heat issue but just putting fans in the case may not help. It really sounds like the Processor is overheating. So check the fan on the heatsink, make sure it is working, spinning, and try blowing out the fins on the heatsink.

i have already checked the heatsink, i cleaned it and put new thermalpaste on it. it worked before until i install does case fan. wich was 15mins ago

just checked the cpu meter and its at 90c and went down to 75celsius

Do you remember what all you touched when you installed the fans? You could also have accidentally loosen something in the process. Does it boot up, and then shut off, or are you hearing a beep sequence?

don't connect your auxilliary fans on the wire that is connected to your hdd

no i haven't, it turns off when windows is loaded and i start a program or something and i changed the psu and it worked after.

the fans are only able to connect to the power cables(hd)
I will probably buy a new heatsink/fan.