The "black hose" has no filter. It is a sump hose & it may or may not have a plastic "eco ball" in there depending on which machine you have. The filter is located at the front of the machine (at the bottom). Look for a small trapdoor & open it. You should see 2 things...a small hose with a plug in the end & a filter. The filter unscrews anticlockwise but before you remove it you must drain the remaning water via the drain hose. Have a bucket on hand! Once the water is drained you can safely open the filter (there will be a small amount of water still in there so put a towel underneath). Check inside for foreign objects & remove whatever you find. Of course it is always possible there could be a small item of clothing or similar stuck in the sump hose, but check the filter first before tearing off hoses. That's the easiest way to go. You could also have a faulty pump, they do wear out....often.
Mike
October 2009