relief valve should be connected to the brake port. See figure 12-44. Operation of the manual lever through five full strokes should pump hydraulic fluid through the relief valve. Leakage at the piston rod gland should not exceed 1 drop at this time. Not less than 0.75 cubic inch of fluid should flow from the relief valve during anyone complete stroke cycle of the manual lever. There should be no evidence of binding at any time during these tests. BRAKE SHUTTLE VALVE Shuttle valve maintenance is generally limited to repairing leakage. External leakage may usually be repaired by tightening the end caps. If this does not stop the leakage, the end cap O-ring should be replaced. Internal leakage can usually be repaired by removing and flushing the unit with clean, hydraulic fluid. Excessive heating is a good indication of internal leakage through a shuttle valve. Excessive cycling of the emergency system pump is also an indication of a leaky shuttle valve. After an emergency system has been operated, all emergency system pressure should be bled off as soon as possible and the normal system restored to operation. AUTOMATIC BRAKE ADJUSTER VALVE Tests are not required on the individual adjuster valve parts. After disassembly, cleaning, inspection, repair or parts replacement, and complete reassembly have been accomplished, perform a bench test to determine whether the brake adjuster valve satisfies the required minimum specifications. Disassembly The brake adjuster valve should be disassembled in accordance with instructions contained in the MIM and/or 03 manual. Check the safety wiring before disassembly to expedite rewiring after reassembly. Cleaning Clean all parts except the nylon insert and O-rings with P-D-680 cleaning solvent. The insert and O-rings will normally be replaced upon each disassembly of the valve. Dry parts with dry, clean, filtered, compressed air. WARNING Do not inhale solvent vapors or direct compressed air against the skin. Failure to observe proper safety precautions could result in injury to personnel. Inspection Perform inspections under a strong light and with magnification. Inspect all threads for crossed, filled, or stripped conditions. Inspect all parts for nicks, scratches, scoring, corrosion, or other damage. Check all drilled passages for obstructions. Repair or Parts Replacement Replace any part that is damaged or does not function properly. During replacement and before actual reassembly, lightly coat all parts with hydraulic preservative fluid; assemble parts while they are wet. Reassembly Reassembly is essentially the reverse of dis- assembly. Directions for reassembly are provided in the MIM and/or 03 manual. Bench Test The bench test consists of a series of tests–proof pressure, thermal crack, shuttle valve opening operation, shuttle valve closing operation, and leakage. Perform these tests in the order listed on a test bench, and not while they are installed in the aircraft. The test bench used must be capable of supplying hydraulic fluid filtered through a 3-micron filter at a maximum pressure of 2,250 psi. Conduct the tests at a room temperature of 70° to 90°F and a fluid temperature of 70° to 110°F. Before you start the test, bleed all air from the unit. After completing the test, remove the valve from the bench. Flush with hydraulic preservative fluid, drip-drain, and plug the ports. The cure date of the oldest scaling device should be rubber-stumped on the body of the valve, and the unit togged with the date and results of the test. To perform the proof pressure test, apply a hydro- static proof pressure of 2,250 psi to the RET (return) port with the BRAKE and PMV (power/manual valve) ports interconnected. Apply this pressure twice and hold for a 2-minute period each time. There should be no evidence of external leakage, failure, distortion, or permanent set. Perform the thermal crack test by applying pressure gradually to the BRAKE port with the RET and PMV ports open until the valve cracks. The residual pressure should not be less than 27 psi. Again, gradually increase pressure at the BRAKE port until the valve cracks. The cracking pressure should be between 30 and 37 psi. There should be no leakage from the PMV port. NOTE: During piston travel a volume of fluid will be displaced through the PMV port. Only the portion of displaced fluid that exceeds 10 cubic centimeters should be considered as leakage. No RET port fluid displacement should be considered leakage. 12-50