yum ignoring cached packaged?

["darrell pfeifer" <darrellpf gmail com>]

I'm updating a rawhide system that hasn't seen an update
in about a month. The yum update managed to download 750 meg
of rpms but didn't have enough disk space to install them.

I ran update on gnome, then kde. Yum used the cached
files. I decided to update yum itself. On the next update
yum rebuilt the sqlite cache. Subsequent yum updates are
now downloading the rpm's again, ignoring about 500 meg
of files sitting in /var/cache/yum.

Is this a bug or expected behaviour?

darrell