For several weeks, shortly after a flush, my toilet would make a loud chirping noise for about 30 seconds. It flushed perfectly and did not have constant running water or any leaks. The noise stopped by itself a few months ago.
-- What was it?
-- Why did it stop?
-- Is some part slowly going bad?
(I found a similar question in the archives the other day, but can't find the thread today for some reason.)