777F Off-Highway Truck Hydraulic System Caterpillar

Gear Pump (Hoist, Brake Charge, Brake Cooling) Efficiency - Test

Usage:

777F JRP

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Table 1
Required Tools
Part Number	Description	Required Amount
4C-9437	Hydraulic Flow Tester	1

This test is designed to determine if a pump is operating within the designed parameters.

Note: This test is only valid for the hoist pump and brake charging pump. The center brake cooling pump is a low pressure pump. The brake cooling pump should not be tested at 6900 kPa (1000.0 psi). The performance of the center brake cooling pump should be checked by comparing the measured pump output versus the minimum flow requirements. Refer to the Specifications, "Gear Pump (Hoist, Brake Charge, Brake Cooling)" of the Hydraulic System module.

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.

Flow loss is used as a measure of pump performance when the flow loss is expressed as a percent of pump flow.

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Table 2
Percent flow loss
[(A − B) ÷ C] × 100 = D
A	Pump flow at 690 kPa (100 psi)
B	Pump flow at 6900 kPa (1000 psi)
C	Pump flow at 690 kPa (100 psi)
D	Percent flow loss

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Table 3
Example
[(A − B) ÷ C] × 100 = D
A	217.6 L/min (57.5 US gpm)
B	196.8 L/min (52.0 US gpm)
C	217.6 L/min (57.5 US gpm)
D	Percent of flow loss
[(217.6 L/min (57.5 US gpm) − 196.8 L/min (52.0 US gpm)) ÷ 217.6 L/min (57.5 US gpm)] × 100 = D
D = 9.6 percent

If the percent of loss is more than 10 percent for the machine test or 15 percent for the bench test, the pump performance is not good enough.

Note: The numbers in the formula are only examples. These numbers are not values for any specific pump nor for any particular pump condition. See the Specifications for the pump flow of a new pump at 690 kPa (100 psi) and at 6900 kPa (1000 psi).

Machine Test

Install a 4C-9437 Hydraulic Flow Tester.
Start the engine.
Run the engine at high idle.
Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi).
Use the values that were measured in Step 4 in Table 2.

Bench Test

If the bench test can be run at 6900 kPa (1000 psi) and at full rpm, determine the percent flow loss.

If the bench test cannot be run at 6900 kPa (1000 psi) and at full rpm, use the following procedure:

Run the pump shaft at 1000 rpm.
Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi).
Use the measurements from Step 2 for the values of A and B in Table 2.
To determine the value of C, use Steps 4.a through 4.b.
1. Run the pump shaft at 2000 rpm.
2. Measure the pump flow at 690 kPa (100 psi).
Use the measurement from Step 4.b for the value of C in Table 2.