Water damage- still works but shuts off

I spilt a very small amount of water on my Mac, I immediately flipped it over and then turned it off. I let it sit for a couple days, under a fan, then in a hot car. Then I took it to an apple technician (so the certificate said on his wall anyways).

He said the battery and the display were not working, and that he opened it up and cleaned it out (I'm assuming with iso propyl alcohol). I went home all depressed, and turned it on as a joke, it came on...

Weeks later, the computer still works, but after I turn it on, it will shut down after about 10-30 mins...

Is there a fan in the computer, could the water have caused some oxidation around the cooling mechanism, and it shuts off because of it's inability to keep cool?

Also it only turns on when I have it plugged in (most of the time)

the battery is still taking charge.

Everything seems to work fine, except it shutting off all the time