I changed oil today and the cap and stem of the filter holder separated when I lifted the cap up; SO I snapped a few pictures. Many have asked about how to separate the parts. These pictures may help. It does NOT twist. There are two rows of tabs. One row on the circumference of the long stem which engage a matching set of tabs on the cap. However, there are four ears that closer towards the center of the cap and these fit into a notch on corresponding tabs on the stem preventing the stem from twisting. Also in the center of the stem there is a pressure relief valve. There are no "O" rings on the stem or the cap where they join.

inside of cap the short ears prevent from twisting



end of stem, you see the notches the tabs insert to prevent twisting; the outer tabs engage with those on the cap to hold inplace

spring loaded relief valve, center of stem

There doesn't seem to be any reason to separate the stem from the cap. There are no serviceable parts in there.