Overheating laptop - any ideas?

[Galdorf]

I have seen this many times it is usually a defective heatpipe they are hard to diagnose best if you carry a replacement to swap out during tests.

 

[ATTech]

Yes, that could be the case. But I'm just saying is check the obvious before you go on an endless hunt for a mysterious short that, statiscally, almost never happens

Actually, it does happen. You're right to first assume an issue with heat dissipation, but from what I've gathered from reading this thread: he's exhausted that kind of testing.