Analysis of The Gear Pump

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The common faults of gear pump in use include small flow, no oil absorption, insufficient pressure and Large Noise, Oil Leakage, Overheating, Abnormal Operation of Oil Pump or Stuck Shaft, Broken Pump, etc. For these Problem analysis and solutions for your reference.

Gear Pump 4035495 for John Deere 790

1.The oil pump does not absorb oil or the flow is very small

This phenomenon may be caused by the following reasons:

  • The oil suction position is too high or the oil level is insufficient;
  • High oil temperature;
  • The oil filter is blocked;
  • The clearance between the gear in the gear pump and the end faces of the front and rear cover plates is large;
  • The sealing performance of gear pump is not good

  • Fill oil in the oil tank and lower the oil suction position;
  • Add a cooler in the oil tank or use air cooling;
  • Clean or replace the filter element of the oil filter;
  • Replace the pump body;
  • Replace sealing elements and fasten connectors

Axial Piston Pump 259-0815 10R-8707 for Caterpillar Excavator CAT 330D 336D

2、 Insufficient pressure

Generally, we can start from the following aspects

  • Whether the pressure of the overflow valve is too low or the overflow valve is damaged;
  • The oil filter is blocked;
  • The viscosity of the oil is too high or the temperature is too high;
  • Wear occurs in the gear pump and the clearance is large;
  • The gear pump body has cracks or leaks;
  • The power of the motor does not match the gear pump

  • Adjust the pressure of the overflow valve or replace it with a new one
  • Clean the oil filter and replace it with a new filter element;
  • No. 20 engine oil is suitable for working at 10-50 ° C ambient temperature. If the oil temperature is too high, a cooling device needs to be installed;
  • Replace the gear pump;
  • In case of leakage, a paper pad can be added between the pump body and the pump cover to fasten the connector. If the pump body has cracks, the pump body needs to be replaced;
  • Select matching motor

Gear Pump 4I-1023 4I1023 for Caterpillar Cat 312 312B 315 315B L 317 317N 318B L 320

3. High vibration and noise

This phenomenon may be caused by the following reasons:

  • The diameter of oil inlet pipe is too small;
  • The oil filter is blocked;
  • The speed is too high;
  • During installation, the gear pump shaft is not concentric with the oil pump or motor;
  • Gear error or two gear axes are not parallel;
  • Inhale air into the pump

  • Replace the oil inlet pipe with large diameter;
  • Clean the filter;
  • Reduce the speed;
  • Adjust the coaxiality between the gear pump shaft and the oil pump or motor to not exceed 0.01mm;
  • More smooth and high-precision gear to ensure that the gear axis is parallel;
  • Check whether air is sucked in and replace the seal

Gear Pump Ass'y 705-51-31060 for Komatsu PC1600-1 PC1600SP-1 PC1800-6 PC650-3

4.Oil leakage from oil pump

The Causes May Be:

  • The oil seal in the pump body is aging and damaged;
  • The seal is damaged due to high pressure in the pump;
  • The shaft head frame spring falls off;
  • The fit between the pump cover and the sealing ring is too loose.

  • Replace the oil seal;
  • Find out the cause and replace the seal;
  • Regrind the sealing surface;
  • Adjust the clearance between pump cover and sealing ring.

Gear Pump XJBN-00965 for Hyundai R290LC-7 R290LC-7A R290LC-9 R300LC-9A

5、 The oil pump does not operate normally or is stuck


  • There are impurities in the pump;
  • Pressure valve failure;
  • The concentricity of gear pump, oil pump and motor coupling is not enough;
  • The axial clearance and radial clearance of the pump body are too small;
  • The needle roller does not rotate flexibly;
  • The concentricity between the cover plate and the shaft is not enough.

  • Check the hydraulic system, replace the hydraulic oil, clean the filter element and replace the gear pump;
  • Replace the spring, remove the dirt from the small hole of the valve body, or replace the valve;
  • Adjust the coaxiality;
  • Adjust the axial or radial clearance;
  • Replace the movable needle roller bearing;
  • Replace the cover plate to make it concentric with the shaft.