TM 5-3805-260-24 9. Check for leakage in the hoses, lines and connections from the emergency brake control valve to  the  dry  air  tank.  Also  check  for  leakage  from  the emergency pilot valve to the double check valve. 10.  Check for leakage in the hoses, lines and connections  from  the  parking  brake  control  valve  to the parking brake chamber. 11.  Check for leakage in the hoses, lines and connections   from   the   brake   control   valve   to   the tractor and scraper air chamber and brake cylinder. 12.  Operate each valve in the accessory circuit separately. NOTE:   The   components   in   the   accessory   circuit   are: differential lock valve, seat suspension, air  horn solenoid valve, and window washer valve. 13.  Check   for   leakage   in   the   hoses,   lines   and   con- nections and components from each valve. NOTE:      During   the   time   the   valves   are   checked   for leakage,   check   the   exhaust   passages   for   restrictions, like mud or dirt. A restriction in an exhaust passage  will prevent or slow the release of pressure air during normal operations. Parking Brake Check 1. Start  the  engine  and  let  the  pressure  go  up  to  the cutout pressure. 2. Lift the bowl (empty). 3. Move the knob on the parking brake control valve to the ON position (pulled out). 4. The    parking    brake    chamber    must    hold    the    rod extended. 5. If the parking brake chamber does not hold the rod, see TROUBLESHOOTING. 6. Move   the   knob   on   the   control   valve   to   the   OFF position (pushed in). 7. The parking brake chamber must release the rod. 8. If  the  parking  brake  chamber  does  not  release,  see TROUBLESHOOTING. TROUBLESHOOTING Item Problem 1. Service Brakes Do Not Engage Correctly. 2. Service Brakes Do Not Release Correctly. 3. Emergency Brakes Do Not Engage Correctly. 4. Emergence Brakes Do Not Release Correctly. 5. Parking Brakes Do Not Engage Correctly. 6. Parking Brakes Do Not Release Correctly. 7. Differential Lock Does Not Engage Correctly. 8. Differential Lock Does Not Release Correctly. NOTE:  If the TROUBLESHOOTING  gives an indication that pressure air is not available at the supply passage(s) of the control valves, loosen the connection at the supply passage and use soapy, water to check for pressure air. If   the   TROUBl.ESHOOTING      gives   an   indication   of leakage    through    a    control    valve(s),    disconnect    the delivery  hose  at  the  end  opposite  the  delivery  passage. Put the end of the hose in a pan of , water to check for leakage. SERVICE BRAKES DO NOT ENGAGE CORRECTLY Causes: a. No  pressure  air  at  the  inlet  passage  of  the  brake control  valve.    Wear  or  damage  to  brake  control valve  permits  little  or  no  pressure  air  at  the  outlet passages.    Wear  or  damage  to  the  components between  the  brake  control  valve  and  the  tractor and scraper air chamber and brake cylinders. d. Wear  or  damage  to  the  air  chamber  and  brake cylinder. e. Wear or damage to the double check valve. f. Brakes have wear or damage. 2. SERVICE BRAKES DO NOT RELEASE CORRECTLY Causes: a. Mud  or  dirt  under  pedal  does  not  let  the  brake control valve release fully. b. Wear    or    damage    to    the    brake    control    valve prevents or slows the release of pressure air from the  lines  to  the  tractor  and  scraper  air  chamber and brake cylinders. 2-146