mt6451 display

I seem to have a problem with the display, I think it's related to overheating.
I've had the laptop for several years now and recently replaced the board and the cpu after someone left it running over a weekend unattended and it died.

Initially everything worked fine after the repairs however, today the display went black when I left it running to install a large software package. When I plugged it into a monitor the display on the monitor there worked fine. Then I shut it off I blew cold air from a can all through the fan and cpu and when I booted it back up I got the display back. I've heard of cpu and mobo failure from overheating but not lcd displays and can find nothing on the internet.
Is that the possible problem, or have I just replaced one bad mobo for another?

 

I'm thinking it has something to do with heat now. I've reseated the cpu and added a bit more heatsink paste. As of right now, it has been running for 24hrs., the display is still up and everything else still works.

 

However, I've just rebooted and no display, which is what makes me think heat. I the brief seconds the fan isn't active, it heats enough to stop the display. But I'm just guessing here, another opinion would be gladly appreciated.