SERVICE MANUAL Fig. 7 Brake Valve Releasing 1 Spring Seat 2 Primary Piston 3 Primary Delivery 4 Primary Exhaust Valve Open 5 Secondary Delivery 6 Secondary Exhaust Valve Open 7 Exhaust Port 8 Secondary Inlet Valve Closed 9 Secondary Supply 10 Relay Piston 11 Primary Inlet Valve Closed 12 Primary Supply 13 Rubber Graduating Spring 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 SPECIFICATIONS. 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  seat.  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) Disassemble  brake  valve;  clean  and  inspect  all  parts. Install  new  parts  where  they  are  found  to  be  worn  or damaged. SERVICE CHECKS Operations Check     delivery     pressure     of     both     primary     and secondary   systems   using   test   gauges   known   to   be accurate.    Depress  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  the brake pedal. After a full application is released, the reading on test gauges  should  fall  off  to  zero  promptly.    It  should  be noted  that  the  primary  system  delivery  pressure  will  be about 14 kPa (2 psi) greater than 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 vehicle should not be operated until necessary repairs have been made and    both    braking    systems,    including pneumatic  and  mechanical  devices,  are operating normally. Always check vehicle   brakes   after   performing   brake work and before returning the vehicle to service. Leakage Test Make  and  hold  a  high  pressure  application.  Check  the exhaust  port  for  leakage.    Using  a  soap  solution  ,  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. Apply  parking  brake  or  block  wheels  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. CTS-4079 - CHAPTER PRITNED Page 6