Question

an old machine become hot faster than a new machine. why

Answer 1

Gears keep them COOL. As machines run faster, speed reducers heat up and their rising temperatures become a bigger concern in designing drives. ... Heat causes a lot of wear and tear on gears, often shortening their life considerably. It doesn't matter whether the heat results from continuous or intermittent operation.

Answer 2

Because they have been working over a long period of time.....
So they get overheated.
It is also due to some damages...