Steve. Tilt the machine onto its back feet, slightly and get someone to pour a glass of water into the drum. Use a torch to see if any water appears and from where.
Also. The drum is retained within a plastic outer cover and if you run your hand around it, feel for any damage. If damage has occurred to the outer plastic surround, allowing water to escape, it would be cheaper to buy new, unless yours is under guarantee.
Check the pump assembly. It is the unit at the bottom on the reverse side of the filter door. Check that TWO hoses are attached. Squeeze the other black rubber pipes around the machine looking and feeling for damage as these can puncture, if debris is stuck within, or if the machine is old, can perish - although rarely...
The rattle may be a metalic item which may be a stud from clothing or a zip tag, etc. which may have made its way to the area between the drum and it's plastic surround. Sometimes these sort of items, coins etc. can be spun with such force that they can rupture the plastic outer drum.
Sorry for being long winded, but explaining something simple still takes alot of words.
If a pipe is leaking this is easily replaced and reletively cheap.
If something has become lodged between the steel and plastic drums and neither has sustained damage, the only option for you to try, is to undo many of the bolts on the underside of the machine's plastic surround which hold it together. this may allow you to pry it open enough to flush out the offending item.
DO THE LAST OPTION OUTSIDE WITH THE MACHINE UP ON BLOCKS.
Good luck.
Davy Mac, June 2009