Message Name:

LEAKAGE AT ENGINE DRAINS

The observed Hydraulic System internal leakage rate is more than the permitted limits.

• Hydraulic-System Pressure Relief Valve 3
• Valve Manifold Pressure-Relief-Valve
• Hydraulic-System 3 Reservoir Temperature Transducer (MT144)
• Hydraulic-System 3 Reservoir Quantity Transducer (MT145)
• Ram Air Turbine (RAT) Hydraulic Pump
• AC Motor Pump 3B (B54)
• Flight Control Unit 1 (A65)
• Flight Control Unit 2 (A66)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Refer to Hydraulic System Internal Leak Check 3 for detailed procedure.

CAUTION: USE TWO WRENCHES WHEN YOU REMOVE/TORQUE THE HOSES/TUBES. USE ONE WRENCH TO HOLD THE FITTING, AND THE OTHER WRENCH TO LOOSEN/TORQUE THE COUPLING NUT. IF YOU DO NOT DO THIS, YOU CAN CAUSE DAMAGE TO THE COMPONENTS.

1. Prepare the hydraulic system 3 for the troubleshooting of the filter-manifold system pressure-relief-valve, on the filter-manifold return t-fitting, disconnect the tubes and install a plug in each tube and two caps on the t-fitting.
   NOTE: If a component is replaced, repeat the procedure to verify the leak rate is acceptable.
2. On the filter-manifold pressure out t-fitting, disconnect the tubes and install a plug in each tube and two caps on the two ports of the t-fitting.
3. On the filter-manifold, disconnect the Pump A and Pump B pressure tubes and install a plug in each tube and a cap on each of the check-valves. Torque all caps and plugs.
4. Remove the dust caps from the pressure and return quick-disconnect couplings. Connect the pressure hose of the hydraulic-power unit to the pressure quick-disconnect coupling and connect the return hose of the hydraulic-power unit to the return quick-disconnect coupling.
5. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
   NOTE: Make sure the reservoir of the hydraulic-power unit has the capacity to hold the hydraulic-system reservoir fluid.
   WARNING: NO PERSON OR EQUIPMENT MUST BE NEAR THE FLIGHT CONTROLS AND THE HYDRAULIC COMPONENTS WHEN YOU PRESSURIZE THE HYDRAULIC SYSTEMS. THE FLIGHT CONTROLS CAN MOVE AND THE HYDRAULIC COMPONENTS CAN EJECT HYDRAULIC FLUID. THIS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO THE EQUIPMENT.
   WARNING: USE THE APPROVED EYE PROTECTION WHEN YOU ARE NEAR THE PRESSURIZED HYDRAULIC SYSTEMS. PRESSURIZED HYDRAULIC FLUID IS DANGEROUS AND CAN CAUSE INJURY TO PERSONS.
6. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.
   CAUTION: DO NOT OPERATE THE HYDRAULIC PUMPS WHEN YOU HAVE A GROUND HYDRAULIC SOURCE CONNECTED TO THE AIRCRAFT. IF YOU DO NOT OBEY THIS INSTRUCTION, THE RESERVOIR WILL FULLY DRAIN INTO THE EXTERNAL HYDRAULIC SOURCE AND CAUSE CAVITATION IN THE PUMP. THIS CAN CAUSE DAMAGE TO THE EQUIPMENT.

   1. If the pressure is out of range, repair and set as required and continue with next step.
   2. If the pressure is within range, continue with next step.

7. Perform a leak check of all the caps/plugs on the filter manifold. Set the EICAS to the hydraulic synoptic page.

   1. If there is leak in caps/plugs, repair or replace as required and do close out.
   2. If there is no leak in caps/plugs, continue with next step.

8. Set the EICAS to the hydraulic synoptic page, check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
   NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

   1. If the fluid temperature is out of limit, repair or replace as required and do close out.
   2. If the fluid temperature is within limit, continue with next step.

9. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
10. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

11. Make sure the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

12. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.003 gpm or 0.384 oz per min (11.4 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the pressure-relief-valve is not more than the permitted limit, go to step 16.
    2. If the leak rate of the pressure-relief-valve is more than the permitted limit, replace the defective filter manifold and continue with the next step.

13. Leave the tubes disconnected and install a plug in each tube and two caps on the t-fitting. Leave the Pump A and Pump B pressure tubes disconnected and install a plug in each tube and a cap on each of the check-valves. Check if the leak rate of the filter manifold pressure-relief-valve is acceptable.

    1. If the leak rate of the filter manifold pressure-relief-valve is more than the permitted limit, repair or replace as required and do close out.
    2. If the leak rate of the filter manifold pressure-relief-valve is acceptable, continue with next step.

14. Remove the plug in each tube and the two caps on the t-fitting. Connect the tubes to the t-fitting. Remove the cap on each of the check-valves and connect the Pump A and Pump B pressure tubes to the check valves.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

15. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

16. Disconnect the drain line from the return quick-disconnect coupling and connect the return hose of the hydraulic-power unit to the return quick-disconnect coupling.
17. Prepare the hydraulic system 3 for the fault isolation of the valve manifold pressure-relief-valve, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
18. Disconnect and plug tubes of filter-manifold. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
19. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
20. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve. Perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

21. Set the EICAS to the hydraulic synoptic page, check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

22. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
23. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

24. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

25. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.006 gpm or 0.768 oz per min (22.7 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the valve manifold pressure-relief-valve is not more than the permitted limit, go to step 29.
    2. If the leak rate of the valve manifold pressure-relief-valve is more than the permitted limit, replace the defective valve manifold and continue with the next step.

26. Leave the plugs on tubes and install caps on fittings.

    1. If the leak rate of the valve manifold pressure-relief-valve is more than the permitted limit, repair or replace as required and do close out.
    2. If the leak rate of the valve manifold pressure-relief-valve is acceptable, continue with next step.

27. Remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes. Connect the Pump A and Pump B pressure tubes to the check valves and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

28. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

29. Disconnect the drain line from the return quick-disconnect coupling and connect the return hose of the hydraulic-power unit to the return quick-disconnect coupling.
30. Prepare the hydraulic system 3 for the fault isolation of the hydraulic-system reservoir 3, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
31. Disconnect and plug the tubes. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
32. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
33. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

34. Set the EICAS to the hydraulic synoptic page. Check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

35. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
36. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

37. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

38. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.003 gpm or 0.384 oz per min (11.4 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the hydraulic-system 3 reservoir is not more than the permitted limit, go to step 41.
    2. If the leak rate of the hydraulic-system 3 reservoir is more than the permitted limit, replace the defective hydraulic-system 3 reservoir and continue with the next step.

39. Prepare the hydraulic system 3, At the valve manifold, remove the plugs from tubes, caps from the fittings, connect the tubes and torque the tubes. At the filter manifold, remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

40. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

41. Disconnect the drain line from the return quick-disconnect coupling and connect the return hose of the hydraulic-power unit to the return quick-disconnect coupling.
42. Prepare the hydraulic system 3 for the fault isolation of the Ram Air Turbine (RAT) hydraulic pump warming circuit, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
43. Disconnect and plug the tubes. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
44. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
45. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

46. Set the EICAS to the hydraulic synoptic page. Check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

47. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
48. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

49. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

50. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.30 gpm or 38.4 oz per min (1136 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the RAT hydraulic pump warming circuit is not more than the permitted limit, go to step 53.
    2. If the leak rate of the RAT hydraulic pump warming circuit is more than the permitted limit, replace the defective valve manifold and continue with the next step.

51. Prepare the hydraulic system 3. At the valve manifold, remove the plugs from tubes, caps from the fittings, connect the tubes and torque the tubes. At the filter manifold, remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

52. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

53. Prepare the hydraulic system 3 for the ACMP 3B hydraulic pump warming circuit, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
54. Disconnect and plug the tubes. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
55. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
56. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

57. Set the EICAS to the hydraulic synoptic page. Check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

58. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
59. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

60. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

61. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.14 gpm or 17.9 oz per min (530 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the ACMP 3B hydraulic pump warming circuit is not more than the permitted limit, go to step 64.
    2. If the leak rate of the ACMP 3B hydraulic pump warming circuit is more than the permitted limit, replace the defective restrictor check valve and continue with the next step.

62. Prepare the hydraulic system 3. At the valve manifold, remove the plugs from tubes, caps from the fittings, connect the tubes and torque the tubes. At the filter manifold, remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

63. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

64. Prepare the hydraulic system 3 for the Brake circuit, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
65. Disconnect and plug the tubes. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
66. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
67. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

68. Set the EICAS to the hydraulic synoptic page. Check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

69. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
70. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

71. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

72. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.091 gpm or 11.7 oz per min (334 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the Brake circuit is not more than the permitted limit, go to step 75.
    2. If the leak rate of the Brake circuit is more than the permitted limit, replace the defective restrictor check valve and continue with the next step.

73. Prepare the hydraulic system 3. At the valve manifold, remove the plugs from tubes, caps from the fittings, connect the tubes and torque the tubes. At the filter manifold, remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

74. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with the next step.

75. Prepare the hydraulic system 3 for the Flight Control circuit, on the valve manifold, disconnect tubes and Install a plug in each tube and a cap on each fitting.
76. Disconnect and plug the tubes. Install caps on the t-fitting. Disconnect tube and install a cap on the pressure out t-fitting. Disconnect and plug the Pump A and Pump B pressure tubes. Install caps on check valves. Torque the tube, caps and plugs.
77. Open the bypass valve of the hydraulic-power unit and set the reservoir select valve of the hydraulic-power unit to the HYD POWER UNIT reservoir position.
78. Energize the hydraulic-power unit and set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Perform a leak check of all the caps/plugs on the filter manifold.

    1. If there is leak in caps/plugs, repair or replace as required and do close out.
    2. If there is no leak in caps/plugs, continue with next step.

79. Set the EICAS to the hydraulic synoptic page. Check that the fluid temperature increases to between 80°F and 100°F (27°C and 38°C) as shown on the hydraulic-power unit temperature gauge.
    NOTE: Operate the hydraulic-power unit in bypass mode until the hydraulic fluid gets to the correct temperature. Follow the hydraulic-power unit instructions to increase the fluid temperature with the hydraulic-power unit.

    1. If the fluid temperature is out of limit, repair or replace as required and do close out.
    2. If the fluid temperature is within limit, continue with next step.

80. Open the hydraulic-power unit bypass valve. When the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off. Disconnect the return hose of the ground hydraulic-power unit from the return quick-disconnect coupling and connect a drain line to the return quick-disconnect coupling. Put the open end of the drain line into a fluid container.
81. Energize the hydraulic-power unit. Set the hydraulic-power unit pressure to 3000±50 psi (20684±345 kPa). Slowly close the hydraulic-power unit bypass valve.

    1. If the pressure is out of range, repair and set as required and continue with next step.
    2. If the pressure is within range, continue with next step.

82. Check that the fluid temperature is between 70°F and 100°F (21°C and 38°C).

    1. If the fluid temperature is out of limit, repair and set as required and continue with next step.
    2. If the fluid temperature is within range, continue with next step.

83. Measure the fluid leak rate at the return drain line for one minute. The fluid leak rate must not be more than 0.60 gpm or 76.8 oz per min (2271 cc per min). Open the hydraulic-power unit bypass valve and when the hydraulic system pressure drops to 0 psi, set the ground hydraulic-power unit to off.

    1. If the leak rate of the flight control circuit is acceptable, then the high leakage must be in the landing gear circuit. Go to step 85.
    2. If the leak rate of the Flight Control circuit is more than the permitted limit, continue with the next step.

84. Check for which flight control component aileron (0.1 gpm per PCU), ground spoiler (0.003 gpm per spoiler pair), elevator (0.1 gpm per PCU), or rudder (0.1 gpm) has high leakage.

    1. If any flight control component has high leakage, replace the defective flight control component has required and do close out.
    2. If flight control component has no leakage, continue with the next step.

85. Check for which landing gear component (LG select valve, door select valve or NLG select valve) has high leakage.

    1. If any landing gear component has high leakage, replace the defective landing gear component has required and do close out.
    2. If landing gear component has no leakage, continue with the next step.

86. At the valve manifold, remove the plugs from tubes, caps from the fittings, connect the tubes and torque the tubes. At the filter manifold, remove the plugs from the tubes, caps from the fittings, connect the tubes and torque the tubes.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

87. Perform the internal leak test of the hydraulic system 3.

    1. If the flow rate is acceptable, do close out.
    2. If the flow rate is not acceptable, continue with next step.

88. Perform the leak test procedure again.
89. Disconnect the drain line from the return quick-disconnect coupling and the pressure line from the pressure quick-disconnect coupling. Install the dust caps on the pressure and return quick-disconnect couplings.
90. Do close out.