Troubleshooting Guide For Gear-Type Hydraulic Pumps

Troubleshooting Guide For Gear-Type Hydraulic Pumps

IDENTIFICATION	CAUSE	CORRECTIVE CHECKS
Sandblasted band around pressure plate bores Angle groove on face of pressure plate Lube groove enlarged and edges rounded Dull area on shaft at root of tooth Dull finish on shaft in bearing area Sandblasted gear bore in housing	Abrasive wear caused by fine particles Dirt or other fine contaminants not visible to the eye	Was clean oil used? Was filter element change period correct? Were correct filter elements used? Cylinder rod wipers in good condition? Cylinder rods dented or scored? Was system flushed properly after previous failure?
Scored pressure plates Scored shafts Scored gear bore	Abrasive wear caused by metal particles Metal or other coarse contaminants visible to the eye	Was system flushed properly after previous failure? Contaminants generated elsewhere in hydraulic system? Contaminants generated by wearing pump components?
Any external damage to pump Damage on rear end of drive gear and rear pressure plate only	Incorrect Installation	Did shaft bottom out in mating part? Any interference between pump and machine?
Eroded pump housing Eroded pressure plates	Aeration - Cavitation Restricted oil flow to pump inlet Aerated oil	Tank oil level correct? Oil viscosity as recommended? Restriction in pump inlet line? Air leak in pump inlet line? Loose hose or tube connection near or above oil level in tank? Excessive operation of relief valve?
Heavy wear on pressure plate Heavy wear on end of gear	Lack of oil	Was oil level correct? Any leaks in piping inside tank? Any oil returning above oil level?
Housing scored heavily Inlet peened and battered Foreign object caught in gear teeth	Damage caused by metal object	Metal object left in system during initial assembly or previous repair? Metal object generated by another failure in system?
Pressure plate black O-Rings and seals brittle Gear and journals black	Excessive heat	Was a valve stuck? Was relief valve too low? Was oil viscosity correct? Was oil level correct?
Broken shaft Broken housing or flange	Overpressure	Relief valve setting correct? Did relief valve function?