when you undo that cap you should pull out a plastic trap piece that is about 4.5 inch long.That should be attached to the cap you unscrewed to gain access.if the cap has come off leaving the filter bit still inside the filter housing you have to try lever it out.sometimes you have to break them out and replace them with a new one.This is because stuff gets jammed in them and people don't clean and inspect them regular enough.when you get the filter out shine a torch in to the filter housing and check the drain pump impeller rotates freely by flicking it around with a long screwdriver
CK, November 2012
