机队运行中偶有发生刹车往复活门堵头处漏油的故障，需更换堵头封圈，当前AMM手册和CMM手册无详细更换步骤，通过和波音沟通，给出了更换封圈的步骤，具体如下.
SR HNA-HNA-25-1988-02B
To replace the packing of the plug, please follow the recommendations below:
1. Perform AMM TASK 32-41-95-000-801 – Brake Shuttle Valve Removal, item 2C.- Prepare for the removal.
2. Remove lockwire from the the plug P/N: 51378 (IPC 32-41-95-01A, item 90) per AMM TASK20-10-44-000-801-Lockwire removal.
3. Remove the plug P/N: 51378 (IPC 32-41-95-01A, item 90). Use an 11/16-inch wrench to remove the plug.
4. Remove packing (IPC 32-41-95-01A, item 95)Â from the plug per AMM TASK 20-10-17-000-801 – O-Rings removal. Discard the removed packing.
5. Install new packing (IPC 32-41-95-01A, item 95 – P/N: NAS1602-904, P/N: NAS1612-4 or P/N: NAS1612-4A) per AMM TASK 20-10-17-400-801 – O-Rings installation.
6. Install the plug with the new packing. Use an 11/16-inch wrench to install the plug in the port of the housing. Tighten the plug to between 105 and 115 in-lbs (refer to CMM 32-40-06, Figure 802- Assembly Torque Limits).
7. Install lockwire (P/N:MS20995C32) on the plug per AMM TASK 20-10-44-400-801 – Lockwire Installation.
8. Perform AMM TASK 32-41-95-400-801- Brake Shuttle Valve Installation, item 3D.(4) – Bleed the hydraulic brake systems. Make sure that there is no leakage from the replaced packing of the plug as you bleed the brake hydraulic system.
9. Perform AMM TASK 32-41-95-400-801- Brake Shuttle Valve Installation, item 3E – Put the Airplane Back to Its Usual Condition.
