770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Gear Pump (Brake, Brake Cooling, Hoist)

Gear Pump (Brake, Brake Cooling, Hoist) - Purge

Table 1

Required Tools
Part Number	Description	Required Amount
6V-4144	Quick Connect Coupler	1
235-7104	Hose As	1
1S-8937	Needle Valve	1

WARNING: Personal injury or death can result from air in the oil for the brake hydraulic system. Air in the system can prevent complete brake application and it is possible that the wheels on the machine can not be stopped.Air must not be in the oil for the brake hydraulic system to function properly.

Personal injury or death can result from machine movement.Place blocks in front of and behind the wheels to make sure the machine does not move while the parking brakes are disengaged.

NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.Dispose of all fluids according to local regulations and mandates.

1. Assemble the following in order to construct a purge hose assembly: one 6V-4144 Coupler, one 235-7104 Hose As and one 1S-8937 Needle Valve .

Location of the quick disconnect near the Control Manifold (Brake Accumulator Charge)



2. Connect the 6V-4144 Quick Connect Coupler to the quick disconnect fitting near the Control Manifold (Brake Accumulator Charge).

3. Overfill the hydraulic tank.

4. Open the 1S-8937 Needle Valve .Opening the valve will allow oil to flow to the suitable container.

5. Pressurize the hydraulic tank to 100 kPa (15 psi). Use a breaker valve in order to prevent the tank from over pressurization.

6. When a steady stream of oil is observed, close the needle valve .

7. Check the oil level in the hydraulic tank. If necessary, depressurize the hydraulic tank and refill the hydraulic tank to the full mark. Repressurize the hydraulic tank to 100 kPa (15 psi). Use a breaker valve in order to prevent the tank from over pressurization.

8. Start the engine and run at low idle for 5 minutes.

9. Stop the engine.

10. Release the pressure from the hydraulic tank.

11. Relieve the pressure on the purge hose assembly by opening the needle valve. Remove the purge hose assembly.

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

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.

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.

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

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

1. Install a 4C-9437 Hydraulic Flow Tester .

2. Start the engine.

3. Run the engine at high idle.

4. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi).

5. 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:

1. Run the pump shaft at 1000 rpm.

2. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi).

3. Use the measurements from Step 2 for the values of A and B in Table 2.

4. 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).

5. Use the measurement from Step 4.b for the value of C in Table 2.

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