TM 5-3825-226-24 STEERING CONTROL VALVE WITH RELIEF VALVE OPEN 4.  Flow control valve.  5.  Pilot valve.  7.  Orifice. When the pilot valve opens, oil flows through orifice (7)  and  past  the  pilot  valve.    The  flow  of  oil  past  the orifice  causes  a  lower  pressure  in  the  chamber  for  the flow control springs.  This lets the pressure of the oil in the inlet passage move flow control valve (4).  Oil from inlet  (2)  can  flow  through  the  holes  in  the  flow  control valve.  This releases the extra pressure from the circuit. When the outside force is gone and the pressure is reduced, the flow control valve and pilot valve return to their normal positions. Left Turn Position The  control  valve  operation  for  a  LEFT  TURN  is similar  to  that  for  a  RIGHT  TURN.    When  the  steering wheel  is  turned  to  the  left,  the  valve  spool  moves  into the valve body.  Pump oil, from the inlet, flows through the  slots  on  the  valve  spool  into  outlet  (I  1).    This  oil then  flows  to  the  cylinders  and  a  LEFT  TURN  is  the result. The  cylinder  pressure  is  felt  through  passage  (12), and against the pilot valve and flow control valve.  The rest   of   the   relief   valve   operation   is   the   same   as   a RIGHT TURN. TROUBLESHOOTING The  5P5224  Pressure  Gauge  Kit  can  be  used  to make the pressure tests of the steering 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  magnet  and  a measuring   rule   (either   for   inches   or   millimeters)   are usable tools. WARNING:  When testing and adjusting the a steering system, move the machine to a smooth horizontal location.  Move away from personnel and machines that are at work.  There must be only one operator.      Keep   all   other   personnel   away   from   the machine. VISUAL CHECKS A  visual  inspection  of  the  steering  system  and  its components   is   the   first   step   when   a   diagnosis   of   a problem is made.  To remove the tank filler cap, slowly turn  the  filler  cap  until  it  is  loose.    If  oil  comes  out  the bleed  hole,  let  the  tank  pressure  lower  before  the  filler cap is removed.  Make the following inspections: 1.    Measure the oil level. 2.    Check    for    air    in    the    hydraulic    oil.        Do    this immediately  after  the  machine  has  been  operated (with the engine still running).  Use a clear bottle or container to get a sample of the oil in the hydraulic tank.      Check   the   sample   to   see   if   there   are   air bubbles in the oil. 3.    Remove  the  filter  elements  and  look  for  particles removed   from   the   oil   by   the   filter   element.      A magnet will separate ferrous particles from nonferrous    particles    (Piston    rings,    O-ring    seals, etc.). 4.    Check  all  oil  lines  and  connections  for  damage  or leaks. PERFORMANCE TESTS Performance  tests  of  the  steering  system  can  be used for a diagnosis of poor performance and to find the source  of  oil  leakage  inside  the  hydraulic  system.    The oil   must   be   at   the   normal   temperature   for   operation when the tests are done. PROBLEM PROBABLE CAUSE RECOMMENDED CORRECTIVE ACTION Steering wheel hard to turn. 1. Mechanical linkage does not move freely. 2. Valve spool does not move freely in its bore. a. Check     mechanical     linkage,     repair     or replace as necessary. b. Check  valve  spool,  repair  or  replace  as necessary. 2-109