I don't think this is the problem... Dirty PCB is a rare case and usually it gives different type of issues.
Yup, also I have done the washing and nothing really happened, about heating up it was normal as I'm in Brazil and the Mobile came from México, the charger is kind of different.
Still, The battery running out is pretty strange. I've done everything, and due to National Policy my mobile cannot be serviced as it is not made in Brazil or authorized by a Import Departament. As they have informed me there was a so called "problem in the mother board", but you know service shops... They will tell you that a bricked phone has to change everything to go back working (and we know this is not the case).
Any ideias? I really have no idea what to do!