SERVICE MANUAL During   next   check,   379-414   kPa   (55-60   psi)   air pressure needs to be maintained at control port (H) and tractor emergency port (G). Connect  air   line   with   gauge   and   shut-off   valve   to tractor service port (F). Open valve to build 345 kPa (50 psi)  pressure  and  shut  off  valve.  Trailer  service  gauge must  show  build  up  pressure.  While  maintaining  steady pressure   of   379-414   kPa   (55-60   psi)   at   pressurized ports, permissible leakage at exhaust port is 25 mm (1") diameter   bubble   in   three   (3)   seconds.   Disconnect   air pressure  to  tractor  service  port  (F).  Trailer  service  port pressure must exhaust to zero. Begin  with  manifold  pressure  supplying  both  control and  tractor  emergency  ports  (G  and  H)  at  681-861  kPa (100-125 psi).  Shut  off  manual  valve  and  disconnect  air source.  Open  manual  valve  slowly  and  allow  manifold pressure  to  bleed  down  to  272  kPa  (40  psi)  and  close manual valve. Air pressure at trailer emergency port (D) should have exhausted to zero. While maintaining steady pressure  of  138-172  kPa  (20-25  psi)  at  control  port  (H) and  tractor  emergency  port  (G),  connect  air  to  tractor service. Open manual valve to build up 345 kPa (50 psi) pressure.  Gauge  at  trailer  service   (E)   must   not   show pressure.    Disconnect    all    air    lines    and    gauges    and remove pipe plugs where used. DISASSEMBLY Refer to Fig. 2 for numbers in parenthesis. After    valve    is    disconnected    and    removed    from tractor, inspect it visually for damage. If casting is broken or shows fractures, replace valve. To disassemble valve, place hand force against end cap (3) while carefully removing snap ring (1) by prying it out  of  the  groove.    (Pulling  exposed  end  of  snap  ring straight out will distort it.)  Spring (19) will push end cap (3) and piston (17) out of body (20). Remove spring (19) and  O-ring  (2)  from  body.  End  cap  (3)  and  piston  (17) can be separated easily. Maintain   finger   force   against   end   cover   (9)   while removing    four    screws    (11)    and    four    washers    (10). Carefully allow spring (12) to free height. Remove  end  cover,  spring  and  valve  (13).  Be  alert for spring (6) to push out spool (7). Remove spool, spring and exhaust  valve  assembly  (5)  from  body.  Remove  O- rings (4), (8), (14), (15), (16), (18) and (21) from pistons, spool  and  cover.    (Remove  metal  retainer  and  rubber seal from assembly (5). CLEANING AND INSPECTION Wash  all  parts  in  clean  mineral  spirits  or  equivalent cleaning solvent and then dry. Examine   rubber   valve   seals   and   O-rings.   Rubber parts must be free of cuts, nicks or tears. Examine  end  cap,  pistons  and  spool.  All  contacting surfaces for O-ring seals must be smooth and round and free of deep scratches, dents or gouges. Valve seats at end  of  piston  tubes  and  spool  must  be  flat  and  smooth showing   no   dents   or   distortion.   Spool   must   not   be fractured or have pieces broken out. Flange on piston for valve assembly (5) must not be dented or bent. Examine valve body and end cover. Castings should be free of cracks and voids. All surfaces for O-ring seals must be smooth  and  round  and  free  of  deep  scratches, dents  or  gouges.    Small  hole  passage  from  control  port into main bore must not be plugged.  Mating surfaces of valve body and end cover flange must not be dented or bent.   Snap   ring   groove   in   valve   body   must   not   be distorted and must be free of corrosion. Valve body seat must    be    flat    and    smooth,    free    of    dents    and    deep scratches.    Examine  springs,  valve  retainer,  snap  ring, screws  and  washers.  Parts  should  be  free  of  distortion and corrosion. Replace parts that show any of the above defects. It is recommended that all rubber parts be replaced with new parts supplied in the repair kit. REASSEMBLY Lubricate   O-rings   and   valve   seal   and   all   O-ring sealing  surfaces  and  bearing  surfaces  on  pistons,  end cap, cover, spool and body. Apply a thin film of Item 3 of LUBRICANT SPECIFICATIONS. Install O-ring (15), valve seal and retainer washer to make  exhaust  valve  assembly  (5).    Install  assembly  (5) into  valve  body  (20).    Install  spring  (6)  with  large  end against  exhaust  valve  retainer.  Install  O-rings   (8)   and (16) on spool (7) and O-ring (14) on end cover (9).  Place spool   on   spring   (6)   with   spool   seat   facing   out.   Place spring (12) and rubber valve (13) on top of spool (refer to Fig. 2 to see position of valve to spring). Align end cover (9) to valve (13) and body (20). Push gently and firmly to compress spring (6) until cover contacts spool. Continue pressing  spool  into  body.  Hold  end  cap  and  install  four washers  (10)  and  screws  (11).  Tighten  screws  to  6-7 N•m (50-60 in lbs) torque. Install spring (19) into valve body (20). Install O-rings (4), (18) and (21) on piston (17). Install O-ring (2) on end cap (3) and mate piston to end cap. Install piston and end cap on spring. Align and push end cap firmly into body and hold to prevent spring from CTS-4079 - CHAPTER XI - Page 5