Hydraulic Pump Repair

Hydraulic pumps operate under demanding conditions and rely on close internal tolerances to produce consistent flow. Wear, contamination, cavitation, overheating, incorrect fluid, and other system problems can reduce pump efficiency and eventually cause failure.

Depending on the pump design, condition, and availability of components, hydraulic pump service may involve:

• Pump inspection and evaluation
• Pump disassembly
• Internal component inspection
• Seal and gasket replacement
• Bearing and wear-component replacement
• Shaft inspection
• Housing inspection
• Replacement of damaged internal parts
• Pump cleaning and reassembly
• Repair-part identification
• Replacement pump identification
• Hydraulic system troubleshooting

Not every pump is economically repairable. Severe housing damage, unavailable parts, extensive internal wear, or the cost of labor may make replacement the better long-term option.

Hydraulic pump problems can appear gradually or develop without warning.

Common symptoms include:

• Reduced hydraulic pressure
• Slow or weak equipment operation
• Loss of performance under load
• Unusual whining, grinding, knocking, or rattling
• Excessive vibration
• Hydraulic fluid leakage
• Pump overheating
• High hydraulic system temperature
• Foamy or aerated hydraulic fluid
• Erratic equipment movement
• Difficulty priming
• Intermittent operation
• Damaged pump shafts or couplings
• Metal particles in the hydraulic fluid
• Repeated seal or component failure

These symptoms do not always mean the pump itself is the only problem. Restrictions, valve problems, internal cylinder leakage, contaminated fluid, incorrect system adjustments, and damaged hoses can produce similar symptoms.

Proper troubleshooting helps prevent replacing a pump without correcting the underlying cause of the failure.

Hydraulic pumps are manufactured in several different designs, each with specific operating characteristics, internal components, and repair requirements.

Depending on the pump and application, Horizon may be able to assist with:

Gear pumps are commonly used in mobile, agricultural, construction, industrial, and material-handling equipment.

Common gear pump problems may include:

• Worn gears
• Internal housing wear
• Damaged bushings or bearings
• Shaft seal leakage
• Reduced flow
• Loss of efficiency
• Shaft or coupling damage
• Excessive noise

Because gear pumps are often relatively compact and cost-effective, the condition and replacement cost should be compared carefully before rebuilding.

Vane pumps use sliding vanes operating inside a rotor and cam ring to create hydraulic flow.

Common vane pump issues may involve:

• Worn vanes
• Damaged cam rings
• Rotor wear
• Seal failure
• Bearing damage
• Contamination
• Pressure loss
• Excessive noise
• Internal leakage

Clean hydraulic fluid and proper inlet conditions are especially important to vane pump performance and service life.

Piston pumps are commonly used in higher-pressure and variable-displacement hydraulic systems.

These pumps may contain pistons, cylinder blocks, valve plates, swash plates, bearings, controls, compensators, and other precision components.

Potential problems include:

• Worn pistons or bores
• Valve plate damage
• Swash plate wear
• Control or compensator problems
• Bearing failure
• Internal leakage
• Pressure instability
• Loss of displacement
• Excessive case drain
• Contamination damage

Piston pump repair requires accurate identification and careful evaluation because internal components and control configurations can vary significantly between models.

Replacing or rebuilding a failed pump without identifying why it failed can result in another breakdown.

Common causes include:

Dirt, metal particles, moisture, degraded oil, and other contaminants can damage internal pump surfaces and increase wear.

Contamination may also indicate that another component has failed and released debris into the hydraulic system.

Cavitation can occur when the pump does not receive an adequate supply of hydraulic fluid. Vapor bubbles form and collapse inside the pump, potentially damaging internal surfaces.

Possible causes include:

• Restricted suction lines
• Clogged strainers
• Low fluid levels
• Incorrect fluid viscosity
• Excessive pump speed
• Collapsed hoses
• Cold hydraulic fluid
• Undersized inlet plumbing

Aeration occurs when air enters the hydraulic fluid. This can cause foamy fluid, erratic operation, noise, overheating, and reduced lubrication.

Air may enter through loose fittings, damaged suction hoses, low reservoir levels, worn seals, or other inlet-side problems.

High operating temperatures can reduce fluid viscosity, damage seals, increase internal leakage, and accelerate pump wear.

Overheating may result from restricted flow, incorrect system settings, internal leakage, poor cooling, contaminated fluid, or continuous operation across a relief valve.

Using fluid with the wrong viscosity or performance characteristics can reduce lubrication, affect pump efficiency, and increase internal wear.

Fluid requirements should be matched to the pump, equipment, operating temperature, and manufacturer specifications.

Hydraulic fluid provides lubrication as well as power transmission. Low fluid levels, contaminated oil, incorrect viscosity, or interrupted pump supply can damage bearings and internal components.

Operating a pump above its rated pressure can damage seals, bearings, shafts, housings, and internal components.

Pressure spikes and incorrectly adjusted relief valves may also contribute to premature failure.

Misalignment, improper shaft rotation, incorrect coupling installation, restricted inlet plumbing, poor mounting, and incorrect port connections can damage a new or rebuilt pump.

A leaking pump does not always require a complete rebuild, but the cause of the leak must be identified.

Common leak points include:

• Shaft seals
• Housing seals
• Port connections
• Flanges
• Gaskets
• Control assemblies
• Case-drain connections
• Cracked or damaged housings

A failed shaft seal may be caused by more than normal wear. Excessive case pressure, shaft damage, misalignment, heat, contamination, or bearing wear can cause a replacement seal to fail again.

Hydraulic pumps naturally produce some operating noise, but a noticeable change in sound may indicate a developing problem.

Whining, knocking, grinding, rattling, or irregular noise may result from:

• Cavitation
• Aeration
• Worn bearings
• Damaged internal components
• Contaminated fluid
• Incorrect fluid viscosity
• Restricted inlet flow
• Coupling problems
• Shaft misalignment
• Excessive pump speed
• Loose mounting hardware

The equipment should be inspected before continued operation causes additional damage.

The decision to repair or replace a hydraulic pump should be based on more than the initial cost.

Factors to consider include:

• Pump age and overall condition
• Extent of internal damage
• Availability of repair parts
• Cost of replacement
• Repair labor
• Equipment downtime
• Replacement lead time
• Availability of an exact replacement
• Condition of the housing and shaft
• Importance of the equipment
• Likelihood of dependable operation after repair

Repairing an original pump may be the best solution when an exact replacement is expensive, unavailable, or requires significant equipment modifications.

Replacement may be better when the pump has extensive damage, limited parts availability, or a replacement is readily available at a reasonable cost.

Installing a repaired or replacement pump without preparing the hydraulic system can lead to another failure.

Before returning the equipment to service, it may be necessary to:

• Inspect the reservoir
• Replace contaminated hydraulic fluid
• Replace filters and strainers
• Clean or flush affected lines
• Inspect hoses and fittings
• Check the pump inlet
• Verify fluid type and viscosity
• Inspect the pump coupling
• Check shaft alignment
• Verify pump rotation
• Confirm relief-valve settings
• Inspect other failed components
• Remove debris from the system

When a pump fails internally, metal particles and other debris may circulate throughout the hydraulic system. That contamination can quickly damage a repaired or replacement pump.

Contact Horizon Hydraulic Sales & Service when a hydraulic pump is leaking, overheating, making unusual noise, losing pressure, or no longer delivering reliable performance.

For the fastest evaluation, provide the pump manufacturer, model or part number, equipment information, photographs, and a description of the symptoms or failure.