SERVICE MANUAL spring  (22).    This  allows  the  rubber  face  of  seal  (16)  to seat    against    the    valve    body    (21)    and    causes    the secondary  piston  exhaust  seat  "G"  to  move  away  from the  rubber  face  of  seal  (16).  This  allows  the  secondary delivery air pressure to exhaust through cavity "K" and to atmosphere around the exhaust port diaphragm (13). MAINTENANCE Every Three Months or 32,000 km (20,000 Miles) Clean   any   accumulated   dirt,   gravel   or   foreign   matter away  from  heel  of  treadle,  plunger  boot  and  mounting plate. Lubricate  plunger,  roller,  roller  pin  and  hinge  pin  using Item 1 in LUBRICANT SPECIFI-CATIONS. Check     rubber     plunger     boot     for     cracks,     holes     or deterioration  and  replace  if  required.    Check  mounting plate for integrity. Free pedal travel should be checked as follows.  Be sure plunger   is   in   contact   with   spring   retainer.      The   stop button should be adjusted so that the roller  and  plunger just contact. Clean exhaust port. Every Year or 160,000 km (100,000 Miles) It is recommended that inlet and exhaust valves, exhaust diaphragm, O-rings and graduating spring be replaced if they show signs of wear or deterioration. Every Two Years or 322,000 km (200,000 Miles) Disassemble  brake  valve,  clean  and  inspect  all  parts. Install  new  parts  where  they  are  found  to  be  worn  or damaged and install repair kit parts. SERVICE CHECKS Operation Check    the    delivery    pressure    of    both    primary    and secondary   systems   using   test   gauges   known   to   be accurate.      Depress   the   pedal   or   treadle   to   several positions   between   the   fully   released   and   fully   applied positions  and  check  the  delivered  pressure  on  the  test gauges   to   see   that   it   varies   proportionately   with   the movement   of   brake   pedal.      After   a   full   application   is released,  reading  on  the  test  gauges  should  fall  off  to zero   promptly.      It   should   be   noted   that   the   primary system delivery pressure will be within 35 kPa (5 psi) of the secondary system delivery pressure with both supply reservoirs at the same pressure. This is normal for these valves. IMPORTANT A change in vehicle braking characteristics or a low pressure warning   may   indicate   a   malfunction   in one   or   the   other   brake   systems,   and although   the   vehicle   air   brake   system may   continue    to    function    the    vehicle should not be operated until the necessary repairs  have  been  made  and both    braking    systems,    including     the pneumatic  and  mechanical  devices,  are operating  normally.    Always   check   the vehicle   brakes   after   performing   brake work   and   before   returning    vehicle    to service. Leakage Test Make    and    hold    a    high    pressure    application.    Check exhaust   port   for   leakage.      Using   a   soap   solution,   a leakage  of  a  25  mm  (1")  soap  bubble  in  3  seconds  is permitted. If  the  brake  valve  does  not  function  as  described,  the valve should either be replaced or repaired. REMOVE 1. Block wheel to prevent vehicle from moving. 2. Drain all air from all reservoirs. 3. Disconnect all supply and delivery lines at brake valve.    Mark  all  air  lines  in  relation  to  valve  to assist reconnecting lines. 4. Remove  fittings  from  valve.    Mark  these  fittings also. 5. Remove valve from chassis. 6. Remove  brake  valve  and  treadle  assembly  by removing three capscrews on outer bolt circle of mounting   plate.      Basic   valve   alone   may   be removed  by  removing  three  capscrews  or  nuts on inner bolt circle. REINSTALL Installation   of   brake   valve   is   basically   the   reverse   of removal.        Be    sure    to    make    service    checks    before returning vehicle to service. CTS-4079 - CHAPTER IV - Page 13