| NOTICE |
|---|
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of all fluids according to local regulations and mandates. |
Note: Pump failure will generally begin with loss of efficiency at low idle, and in conditions that have high oil operating temperature. If the pump efficiency improves after increasing the speed of the engine, or after the oil is allowed to cool, test the pump first.
For any pump test at a given rpm, the pump flow at 690 kPa (100 psi) will be larger than the pump flow at 6900 kPa (1000 psi). The difference between the pump flow of the two operating pressures is the flow loss.
| Method for determining flow loss | ||
| Pump flow at 690 kPa (100 psi) | ||
| - | Pump flow at 6900 kPa (1000 psi) | |
| Flow loss | ||
| Example of determining flow loss | ||
217.6 L/min (57.5 US gpm) | ||
| - | 196.8 L/min (52.0 US gpm) | |
20.8 L/min (5.5 US gpm) | ||
The flow loss is used to measure the pump performance. Flow loss is expressed as a percent of pump flow.
| Method of determining percent of flow loss | ||||
| Flow loss (L/min or US gpm) | 100 | = | Percent of flow loss | |
| Pump flow at 690 kPa (100 psi) |
||||
| Example of determining percent of flow loss | ||||
20.8 L (5.5 US gal) |
100 | = | 9.5% | |
217.6 L/min (57.5 US gpm) |
||||
If the flow loss is higher than 10 percent, the pump is not functioning correctly.
Machine Test
Install a flow meter. Run the engine at high idle. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). Use these values in the formula that is in Table 5.
| Pump flow at 690 kPa (100 psi) |
|||||
| - | Pump flow at 6900 kPa (1000 psi) |
100 | = | Percent of flow loss | |
| Pump flow at 690 kPa (100 psi) |
Bench Test
If the bench test can be run at 6900 kPa (1000 psi) and at full pump rpm, determine the percent of flow loss by using the formula in Table 6.
If the bench test cannot be run at 6900 kPa (1000 psi) and at full pump rpm, run the pump shaft at 1000 rpm. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). Use these values in the top portion of the following formula. For the bottom portion of the formula, run the pump shaft at 2000 rpm. Measure the pump flow at 690 kPa (100 psi).
| Pump flow at 690 kPa (100 psi) |
|||||
| - | Pump flow at 6900 kPa (1000 psi) |
100 | = | Percent of flow loss | |
| Pump flow at 690 kPa (100 psi) and at 2000 rpm |