TM 5-3805-260-24 HYDRAULIC SYSTEM The   5S5123   Hydraulic   Testing   Group   is   used   to make  the  pressure  test  of  the  hydraulic  system.  Before any    tests    are    made,    visually    inspect    the    complete hydraulic  system  for  leakage  of  oil  and   for   parts   that have   damage.   For   some   of   the   tests,   a   timer   and   a measuring  rule  (either  for  inches  or  for  millimeters)  are usable tools. WARNING:    When    testing    and    adjusting    the hydraulic    system,    move    the    machine    to    a    smooth horizontal location. Move away from machines that are at work    and    any    personnel.    There    must    be    only    one operator.  Keep  all  other  personnel  either  away  from  the machine    or    where    the    operator    can    see    the    other personnel. VISUAL CHECKS A  visual  inspection  of  the  hydraulic  system  and  its components   is   the   first   step   when   a   diagnosis   of   a problem is made. Stop the engine, lower the bowl to the ground  and  when  the  oil  is  cool  so  any  pressure  in  the tank  will  be  at  a  minimum,  make  the  inspections  that follow: 1. Measure the oil level. Slowly turn the filler cap until it is loose to let  the  tank  pressure  lower  before  the  filler cap is removed. Look for air in the oil in the tank. 2.  Remove  the  filter  element  and  look  for  particles removed from the oil by the filter element. A magnet will separate    ferrous    particles    from    non-ferrous    particles (piston rings, O-ring seals, etc.). 3. Check all oil lines and connections for damage or leaks. OPERATION CHECKS Checks of scraper operation can be used to find the source  of  oil  leakage  in  the  hydraulic  system.  The  oil  in the hydraulic system must be at an operating temperature of 100° to 1200F (380 to 400C). Drift of Bowl Cylinders Check the drift of the bowl cylinders. Lift the bowl 6 to 10 in. (152 to 254 mm), then move the control lever to the  HOLD  position.  After  three  minutes,  put  a  mark  on the side of the bowl at the bottom of the draft arm 6 in. (152  mm)  from  the  front  of  the  bowl  side.  After  five minutes, make the measurement for drift. Drift on a new machine is not more than .31 in. (7.9 mm). If the drift is too much: 1. Check the carry check valves. 2.   Check   the   piston   seals   in   the   bowl   cylinders. MEASURING DRIFT UOF BOWL CYLINPUEHR (Typical Example) Travel Time of Bowl Cylinders Lower the bowl to the ground. Run the engine at high idle  rpm.  Use  a  stop  watch  to  find  the  time  needed  to fully lift the bowl. The time to lift the bowl from the ground to maximum height is approximately 2 seconds. If the travel time is not correct: 1. Check pump efficiency. 2. Check the settings of the relief valve for the bowl and ejector circuits. 3. Check the operation of the bowl valve spool in the control valve for the scraper. 4. Check the piston seals in the bowl cylinders. Drift of Door Cylinder The  check  valve  for  the  door  lets  oil  go  to  the  ejector cylinder  and  the  door  cylinder  while  the  ejector  moves. The check valve keeps the door closed at the time the bowl is loaded. If the door opens during the load operation: 1. Check for dirt under the check valve. 2.  Check  for  a  broken  valve  spring  in  the  check valve. 3.  Make sure valve moves freely in the valve body. Travel Time of Ejector and Door Lift  the  bowl  approximately  6  in.  (152  mm).  Make sure  the  door  is  closed.  Run  the  engine  at  high  idle. Hold the ejector control lever in the FORWARD position. Use a stop watch to find the time to fully open the door and to move the ejector forward. 4-25