it closed when running. is that normal or should i replace it?
not sure but does it twist first?
the case twists to get the top filter out.
but the one underneath appears to just pull out.
its a while since i have done one to be honest. lets see if anyone else has had one in bits more recently.
must have been case i was thinking of, wonder if its just stuck with dirt, or perhaps slightly melted if motor has got hot, try rocking it. 