Defeature not removing parts

Hello;

       I had a co-worker show me the defeature tool, but it doesn't seem to be working as designed. I check

to remove internal parts, but then end up deleting them all myself after I've done the defeature. Am I doing

something wrong, or is this tool just not fully developed yet. It's within an assembly, and the components are

touching one another.

Thanks in advance for any input;

Rob_D SW 2012 Sp3

SolidworksGeneral