TM 1-1500-204-23-1 (2) Inspect     lining     recesses     in     piston, center  carrier,  and  anvil  for  indications  of  wear  which could  cause  loss  of  lining.    Wear  of  anvil  lining  recess circumference   in   excess   of   0.005   inch   is   cause   for replacement. (3) Examine  piston  cavity  for  corrosion, excessive  wear,  or  for  being  out-of-round.    When  light corrosion extends more than 9/16 inch into piston cavity, or heavy corrosion Is evident, replace brake assembly. NOTE Corrosion is usually found in carrier housing     and     in     piston     cavities. Corrosion    in    magnesium    can    be Identified by the rough honeycombed appearance of the pit. Pits are usually filled with a yellow or gray   powder.      Heavy   corrosion   is defined   as   pits   that   exceed   0.025 inch   in   diameter   or   grouped   with three or more pits of any diameter in an area of 1/4 Inch square. e. Corrosion  Treatment  of  Brake  Assemblies. Brake  assemblies  are  manufactured  from  magnesium, aluminum, and steel Most assemblies have magnesium housings    which    are    very    susceptible    to    corrosion, especially in piston cavities.  Treat the surface using the following procedures. (1) Remove sharp edges of corrosion pits with     crocus     cloth,     Federal     Specification     P-C-458, lubricated with hydraulic fluid, MIL-H-5606. (2) Rework  minor  dents,  nicks,  burrs,  or gouges  to  break  all  sharp  edges  of  indentations  which might result in a concentration of stress.  Use a smooth cut    hand    file    to    accomplish    this,    followed    by    fine abrasive    paper,    Federal    Specification    P-P-101,    to remove tool marks. (3) Condemn brake assemblies that have deep   scratches,   gouges,   or   cracks   exceeding   limits established In applicable aircraft maintenance manual. (4) Accomplish surface treatment as outlined in TM 43-0105. f. Repair and Replacement of Brake Assembly Components.        Repair    or    replace    brake        assembly components in accordance with the applicable maintenance manual and the following general procedures: CAUTION Care  must  be  used  when  installing seals and cups to prevent damage to feathered edges. (1) Replace  all  seals,  cups,  and  O-rings on   an   availability   basis   when   assembling   brakes   to prevent possible leakage and brake failure. (2) Apply   a   light   coat   of   insulating   and sealing   compound,   MIL-I-8660,   to   surface   of   piston cavity and to O-ring or cup seal. (3) Replace disks that have cracks extending  through  disc.    Any  single  crack  that  extends through   thickness   of   brake   disk   shall   be   reason   for replacement.  Minor surface cracks and heat checks are normal and are not cause for replacement. (4) When necessary to replace one lining because of wear, all linings shall be replaced.  Replace linings when any lining thickness is less than 1/16 inch, or shows indications of being overheated. g. Brake  Assembly  Servicing.    Service  brake assemblies in accordance with the applicable maintenance    manual.        The    following    are    general procedures for all aircraft. (1) Check for leaks while system Is under operating pressure. NOTE Tighten loose fittings with the pressure off. (2) Check  all  flexible  hoses  carefully  for swelling, cracking, or soft spots, and replace if evidence of deterioration is noted. (3) Maintain  the  proper  fluid  level  at  all times  to  prevent  brake  failure  or  the  introduction  of  air into the system. h. Bleeding   Brakes.      Air   in   the   system   is indicated by a spongy action of the brake pedals.  If air is   present   in   the   system,   remove   it   by   bleeding   the system.    There  are  two  general  methods  of  bleeding brake system.  Bleeding from the top downward (gravity method) and bleeding from the bottom upward (pressure method).    Each  method  is  explained  in  the  following paragraphs. 9-9