5 Signs Your Gear Pump Needs a Rebuild

1. Reduced Flow Rate

This is the most common and most measurable sign of wear. When internal clearances increase — due to gear tooth erosion, bearing wear, or housing scoring — fluid begins to slip backward through the pump instead of being pushed forward. The result is a measurable drop in gallons per minute (GPM) at the same motor speed and pressure.

If you're monitoring flow with an inline NAPCO DYN series flow meter, you'll see this trend before it becomes critical. A 10–15% drop from baseline flow at the same operating conditions is a strong signal that internal parts are wearing.

2. Increased Noise or Changes in Sound

A healthy gear pump produces a consistent, low-frequency hum. As bearings wear or gear tooth profiles degrade, you'll notice a change in the sound: louder operation, rattling, clicking, or a metallic grinding tone. Experienced operators can often hear a problem before instruments detect it.

Cavitation — caused by insufficient suction pressure or air leaks — produces a distinctive crackling or popping noise, like gravel in the pump chamber. While cavitation isn't always a rebuild issue (it can be a system design problem), repeated cavitation accelerates gear and bearing wear, leading to a rebuild sooner.

Any sudden change in pump noise warrants an immediate inspection. Don't wait for the scheduled maintenance window — open the non-drive side bearing housing and visually check the gears and chamber.

3. Visible External Leaks

Fluid weeping from the shaft seal area, gasket joints, or bearing housings is a direct indicator that seals have degraded. In a properly assembled pump, seals contain process fluid within the pump chamber while grease lubrication protects the bearings from the outside.

When high-pressure seals lose their lip contact — whether from normal wear, chemical degradation, or heat damage — fluid migrates past the seal and becomes visible at the weep holes or shaft exits. This is not a minor issue: once seals fail, bearing contamination follows quickly, and bearing failure leads to shaft damage and catastrophic pump failure.

NAPCO repair kits include all four high-pressure seals, four low-pressure seals, and gaskets — everything needed to restore the sealing system. See the Repair & Parts page for seal orientation details.

4. Excessive Vibration

Vibration that exceeds the pump's normal operating baseline indicates mechanical imbalance. In a gear pump, this is typically caused by bearing wear (allowing shaft play), gear damage (uneven tooth profiles), or foreign object damage (debris lodged in the gear mesh zone).

Increased vibration accelerates wear on every component in the pump — gears, bearings, seals, and the housing itself. If left unchecked, vibration can cause shaft fatigue cracking and permanent housing damage that a repair kit alone cannot fix.

If you detect elevated vibration, reduce operating speed if possible and schedule a rebuild promptly. NAPCO pump housings are designed to last through multiple rebuild cycles, but only if the underlying issue is caught before shaft or housing damage occurs.

5. Rising Motor Current (Amps)

If your motor drive reports increasing current draw at the same operating conditions (same RPM, same pressure, same fluid), the pump is working harder to deliver the same output. This can result from bearing drag (worn bearings creating friction), internal binding (damaged gears or foreign material), or seal drag (improperly installed or swollen seals).

Rising amps is an early warning that often precedes the more obvious symptoms like noise and vibration. If your system includes a variable frequency drive (VFD) or motor monitoring, track the amp trend over time. A consistent upward trend at constant operating conditions means the pump's internal resistance is increasing — and a rebuild is approaching.

What to Do When You See These Signs

The advantage of NAPCO rotary gear pumps is that a rebuild is a straightforward field operation. You don't need to remove the pump from the pipeline, ship it to a service center, or wait weeks for factory repair. With a NAPCO repair kit and standard hand tools, your technician can have the pump back in service in 2–4 hours.

The best practice is to keep a spare repair kit on-site for each pump in your system. When you see the warning signs, you're ready to act immediately — no ordering delays, no production losses waiting for parts to arrive.

Watch our complete three-part repair kit installation video series on the Field Rebuild Advantage page, or read the step-by-step procedure on the Repair & Parts page.

Related Resources

• Field Maintenance for Rotary Gear Pumps — Preventive maintenance schedules and procedures
• Nitrile vs. Viton Gears: Material Selection Guide — Choose the right elastomer for extended gear life
• Rotary Gear Pump 101: The Complete Beginner's Guide — Understand the fundamentals
• Maintenance Guidelines — Lubrication, gasket adjustment, and seal orientation