go bad vs go down

go bad and go down both are verbs.

Word	Noun	Adjective	Verb	Adverb
go bad	No	No	Yes	No
go down	No	No	Yes	No

As verbs, go down is a hyponym of go bad; that is, go down is a word with a more specific, narrower meaning than go bad:

Other hyponyms of go bad include crash, blow, blow out, burn out, misfire, malfunction, misfunction.

go bad (verb)	go down (verb)
become unfit for consumption or use	grow smaller
stop operating or functioning	stop operating
	be defeated
	be ingested
	go under
	disappear beyond the horizon
	move downward and lower, but not necessarily all the way
	be recorded or remembered