Water pressure makes the unit kick on and off. Somehow water is draining back into the pump casing, check the flapper on the check valve inside the discharge elbow, it may not be closing properly or may be obstructed allowing waste water to drain back into the pump. Also check the flapper on the flush valve inside the toilet tank (water closet) the flapper may be leaking water into the bowl and from the bowl into the pump casing sitting behind. As far as making a loud noise, there could be a blockage on the drain pipe, blade or impeller. The discharge pipe may be loose, not clamped against the wall and is rattling against the wall when in use.