Just bought = warranty. Why are you doing all this work?
I'm left to guess the unit was a dead one and you got it to fix. From the sounds of this I would be changing the motherboard and testing the battery as it might be worn out.
I bought a dell 1558 studi laptop and when I turned it on the fans were running like crazy, I installed speed fan and the cores (i5) were at 60 deg at idle.
So I thought, hmm new thermal paste.
Bought some Arctic silver, cleaned it with the Arctic cleaners and skimmed it on as usual.
I replaced the GPU and 2 smaller chips thermal stickers with Pyobia 7wt and slapped it back togther - jobs a good un.
But when it turns on from stone cold, windows starts up and goes to desktop. I can run speedfan and the cores are at 45degs, the fans then kick in successively faster and then the sceen goes black - computer still powered up fans running.
If I then restart it takes less time for the screen to go black - fans now running at vmax
It will happily sit in the Bios screen like a champ, (fans on max mind).
Is it goosed? sometimes It flickers a BSOD but I dont have time to read it before it pegs out.