Overheating issue on the GPU

Nov 3, 2018
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I had a AMD radeon r9 270( not X) yesterday and i got it overheated when im playing PUBG
it run in 36-45° when i leave it at idle and it increase to 104° and my PC shut down immidiatly
any idea how to decrease the temp ?
btw, my spec :
i3 3240
6 gb ram
r9 270 OC
400W PSU
 
Nov 3, 2018
5
0
10

I removed the side panel and yes, i have a fan on the back of the case
do you think my PSU is too weak to carry my rig ?
 
Nov 3, 2018
5
0
10

so, i need to equip another fan ?
where should i put the fan ?
and do you think 400w PSU is the problem ?