According to manga #1, page 29, as the robot dealer took him, he was silent because "he hadn't learned how to cry yet ." The 60s series does not have him crying out of sadness, but tape 8 has him fighting a fire with a flood of tears:


Manga #5 page 109 has a similar scene, except that he
is crying out of sadness. As does page 128 of the same issue.
He is depicted sweating on numerous occasions, but this is likely
to show stress or emotion, rather than actual sweat.