how can i fix the pump a myson compact cp53?

please help dont know anything about plumbing or electrics but my pump has started rattling lately very loud. I found if the octagnal screw is turned a little it leaks water but turning back it sometimes stops the noise(something like moving an ariel on your tv)so to speak. when its at level 2 it doesnt make as much noise but at level 3 it does. All i want to know is do i need to get a new pump or can it be fixed by something very simple? any answers are appreciated
many thanks