ENGINE DIAGNOSTIC TEST PROCEDURES Section 6 II.  AIR INDUCTION SYSTEM PRESSURE TEST General The  most  common  cause  of  engine  failure  is  dirt.  Even though  an  air  cleaner  element  itself  is  properly  serviced per   the   specific   Operation   and   Maintenance   Manual, there  are  other  areas  in   the   induction   system      which must be maintained.  The importance of pressure testing the  air  induction  system  cannot  be  emphasized  enough with   present-   day   high   speed   diesel   engines.      An   air induction leak on the suction side, no matter how small, can  cause  an  engine  failure  and  must  not  be  tolerated. Test   for   leakage   in   the   air   induction   system   using   a manually  regulated  compressed  air  supply,  0-103  kPa (0-15  psi)  pressure  test  gauge,  tube  fittings,  duct  tape, paint brush and soap solution. Test Procedure 1. Block off air inlet pipe or completely mask off the outer  diameter  of  air  cleaner  element  air  inlet with duct tape. NOTE:   Air systems having air cleaners  with  reverse flow must be blocked at the air intake pipe. 2. Disconnect the air cleaner restriction indicator or tubing   at   the   air   cleaner.      Install   a   tee   and connect the indicator or tubing and the pressure test gauge. 3. Remove  a  pipe  plug  from  the  intake  manifold. Connect the manually regulated compressed air supply to the manifold. 4. Introduce   air   to   establish   that   34   kPa   (5   psi) pressurization has been achieved by reading the pressure  gauge.    If  improper  pressure  is  seen, adjust the regulator.   A  constant  supply  of  air  is needed   to   compensate   for   air   loss   out   open exhaust valves. 5. Coat  the  following  areas  with  the  soap  solution and   check   for   leaks.        Leaks    will    cause    air bubbles to form. a. Air  cleaner  body  surface  around  the  outlet pipe. b. Air  cleaner  outlet  pipe  to  air  cleaner  body junction. c. Fitting  and  line  connection  from  air  cleaner outlet  to  restriction  indicator   including   the bottom of the indicator. d. All  clamped  hose  and  gasket  connections between    air     cleaner     outlet     and     intake manifold.        This    includes    connections    at turbocharger, when applicable. e. Surface of all air induction piping and hoses between   air   cleaner   and   intake   manifold including the manifold gasket area. f. When   applicable,   the   air   compressor   air inlet piping from the air cleaner tube to and including the fitting and the gasket. g. When applicable, the piping to the intercooler. 6. No leakage is permitted between air cleaner and turbocharger     (suction     side)     in     turbocharged applications.  If leakage at the joints is detected, tighten  hose  clamps.    If  leakage   still   persists, remove  the  parts  to  determine  the  cause.    Re- place parts as necessary using the latest clamps and   torques   specified.      Retest   the   corrected area. NOTE:   Any    leaks    found    in    air    induction    system could    have    allowed    dirt    to    enter    engine.        Dirt entering   engine   can   cause   high   oil   consumption because    of    badly    worn    or    broken    piston    rings, excessive    blue    smoke,    turbocharger    compressor wheel pitting and erosion.  If any leaks are  found  in the   air   intake   system,   you   can   check   the   internal condition   of   the   engine   by   running   a   crankcase pressure check. Visually inspect the following: 1. Inspect air cleaner housing externally for damage or distortion which could allow unfiltered air to enter the engine.  Also, inspect to see that the unloader valve is in place and not plugged by foreign material. 2. Inspect air cleaner housing internally for damage to    baffles,    end    seal    movement    indicated    by polishing where end seal contacts the air cleaner housing.  End seal movement indicates dirt may have    passed    the    air    cleaner    element    and entered the engine. 3. Inspect  air  cleaner  element  for  holes,  damaged seals, element sooting, end cap denting because of overtightening or damage during servicing. 4. Inspect   hoses   and   clamps   for   tightness   and positioning over sealing beads. CG ES-2404 Printed in United States of America Page 5