Could it be related to:
1) A bent (binding) main shaft?
2) Bad bearing(s)?
3) Worn out swash plate?
4) Worn out ball bearings in the swash plate?
5) Tail rotor gear mesh?
Any number of those type things.
In my case; my hacker brushless ran cool with out the body. Once I put the body on, it would overheat within 3 minutes and begin shutting down. I ran across some pictures within someone’s gallery where they had cut out the windows on the stock body. So, I did the same with the addition of some stylish holes in the bottom. Bingo! Runs cool as a cucumber and in my humble opinion, it looks better too.
Just some stuff to think about,