Hello dear Sifus. Did anyone encounter a problem where the laptop will automatically shut down while gaming? It happens very frequently in Dota 2 but less frequently in games like GTA 4

. Initially I thought it was an overheat issue so I clear out the air vent using a compressed air cannister and removed the bottom cover to clear out dust. The problem still persist and the temperature I assume should be average when gaming (Temperature recorded using Open Hardware Monitor):
Maximum Temperature recorded while playing Dota 2 before laptop crashing
Core 1: 75C
Core 2: 77C
Core 3: 70C
Core 4: 68C
GPU: 65C
HDD: 43C
Temperature recorded minutes after turning on laptop and entering game
Core 1: 65C
Core 2: 67C
Core 3: 59C
Core 4: 60C
GPU: 58C
HDD: 42C
Doesn't seem like an overheat issue to me. Could it be that I have a faulty motherboard/GPU? Bought this laptop for almost a year and half and this issue only came up recently.. The specs are as below:
Laptop model: Lenovo Ideapad Y400
Processor: Intel® Core i7-3630QM CPU @ 2.40GHz 2.40 GHz
RAM: 8.00 GB
System type: 64-bit OS, x64-based processor
OS: Windows 8.1 Single Language
Methods I tried:
Checked Integrity of game cache (Dota 2)
Cleared air vent with compressed air cannister
Remove back cover to wipe off dust and from fan
Check fan to ensure fully functional
Constantly using Dust removal feature to maximize fan speed
Sometimes it crashes only minutes after I on my laptop and enter the game, sometimes it takes 40-50 minutes before acting up. Games other than Dota 2 takes a longer time before crashing. Is there any other ways I could try before sending it to a Lenovo shop this weekend? Any suggestions or help would be much appreciated thank you!!!!

It doesn't seem to be overheating problem to me... but if you're already out of warranty probably you want to replace the thermal paste to avoid any kind of temperature spike during usage. Other than that, I can only imagine something went wrong with the power supply or VRMs.... It probably worth to check out if the thermal pads for the VRAM and VRMs are in good contacts as well... Do you game with battery on or off?