You may have only 400 hrs, but that tractor is still 12 or more years old. If you haven't changed the hydraulic filter in a while, this may be a good time. Probably no fun to access behind the loader frame, but I'd suggest you also replace the hose clamps on the suction hose just before the filter base. You could try to tighten the existing clamps, but my experience with the cheap factory units is that a thick coat fo factory paint combined with a bit of age leaves them difficult, at best, to adjust very effectively.