is there a general rule of thumb for overheating??

[schofield]

is there a general rule of thumb for overheating?

like if the esc is hot and not your motor, it "generally" means?
or
if you motor is hot but your esc is not, it "generally" means?

i was asked by a friend today and did not have an answer.
i know his would not be a solve all, but just kind of a general rule of thub.