It is imperative that all disassembled parts be handled with extreme care. When necessary, clean each part individually in kerosene or other solvent which will depend upon the liquid being pumped. Start inspection by removing the screws holding the cover to the body. A pump which has been in service for some time usually refuses to release its cover by finger pressure alone. The cover will lift off its flange if the exposed end of the drive shaft is tapped lightly with a mallet or on a wooden bench.
Greater clearance is a result of wear or scrubbing of the teeth on the chamber wall.
This means metal has been scrubbed off both the gear tips and the wall. When pumping, hydraulic and mechanical forces tend to separate the gears and force the gear tips against the walls. For the gears to shift to this wear position, the shaft bearings, normally holding gears in alignment, must also be worn. Check bearing wear. Since the idle shaft bearings are subjected to greater loads, they normally show greater wear.