ENGINE  TROUBLESHOOTING “Diagnosing” may be defined as a systematic means   of   identifying   a   problem   by   using   all available   information   and   facts.   Usually,   the Equipment   Operator   will   be   able   to   tell   the symptoms, such as the engine lacks power, uses excessive  oil,  has  low  oil  pressure,  or  makes certain noises. Some internal engine problems may be found by listening for unusual noises and knocks or by examining  the  exhaust  gases  for  indications  of incomplete   combustion.   Then   too,   placing   an artificial  load  on  an  engine  can  emphasize  certain noises;  for  example,  applying  the  brakes  and partially  engaging  the  clutch  with  the  vehicle transmission  in  high  gear.  In  this  manner,  the engine   operating   under   a   load   can   be   heard without  the  interference  of  body  noises. There are also other tricks of the trade that a  mechanic  may  use,  such  as  feeling  the  oil  or shorting out the spark plugs to get an idea of the source  of  trouble. EXCESSIVE  OIL  CONSUMPTION Excessive   oil   consumption   would   probably first  be  noted  by  the  Equipment  Operator  who has  to  add  oil  to  maintain  the  proper  oil  level. There  are  two  main  causes  of  excessive  oil consumption:  external  leakage  and  burning  in  the combustion   chamber. External  oil  leaks  can  often  be  detected  by inspecting  the  seals  around  the  oil  pan,  valve covers,  timing  gear  housing,  and  at  the  oil  line and  oil  filter  connections. The burning of oil in the combustion chamber usually produces a bluish tinge in the exhaust gas. Oil  may  enter  the  combustion  chamber  in  two ways:  (a)  through  clearances  caused  by  wear between the intake valve guides and stems and (b) around  the  piston  rings. Excessive  oil  consumption  caused  by  worn valve  guides  or  stems  may  be  indicated  by  too much  carbon  on  the  undersides  of  the  intake valve. In this case, it is usually necessary to install valve  seals,  new  valve  guides,  or  new  valves.  If excessive  oil  consumption  is  caused  by  worn  rings or worn cylinder walls, the supervisor may have the  mechanics  do  a  complete  engine  overhaul. LOW OIL PRESSURE Low oil pressure often indicates worn engine bearings. Worn bearings can pass so much oil that the oil pump cannot maintain oil pressure. Other causes of low oil pressure include a weak relief- valve  spring,  a  worn  oil  pump,  a  broken  or cracked oil line, or a clogged oil line. Oil dilution, foaming, sludge, insufficient oil, incorrect oil, or oil made too thin by the engine overheating will also  cause  low  oil  pressure. ENGINE NOISES A   variety   of   engine   noises   may   occur, Although  some  noises  have  little  significance, others can indicate serious engine trouble that will require  prompt  attention  to  prevent  major  damage to the engine. A listening rod can be of help in locating the source of a noise. The rod acts somewhat like the stethoscope a doctor uses to listen to a patient’s heartbeat or breathing. When one end is placed at the ear and the other end at some particular part  of  the  engine,  noises  from  that  part  of  the engine will be carried along the rod to your ear. By  determining  the  approximate  source  of  the noise,  you  can,  for  example,  locate  a  broken  or noisy  ring  in  a  particular  cylinder  or  a  main bearing  knock. Valve  and  Tappet  Noise Valve  and  tappet  noise  is  a  regular  clicking sound  that  increases  in  intensity  as  the  engine speed  increases.  The  cause  is  usually  excessive valve clearance. A feeler gauge inserted between the valve stem and lifter or rocker arm will reduce the  clearance,  and  the  noise  should  decrease.  If the  noise  does  not  decrease  when  the  feeler  gauge is  inserted,  it  is  probably  caused  by  weak  lifter springs, worn lifter faces, lifters loose in the block, a  rough  adjustment-screw  face,  a  rough  cam  lobe, or possibly the noise is not from the valves at all. A noisy hydraulic valve lifter maybe sticking because  of  dirt  in  the  ball  or  disk  valve.  When this  happens,  you  must  disassemble  the  lifter  and clean   all   the   parts   in   a   clean   solvent.   Then reassemble the lifter and fill it with clean, light engine  oil. Connecting  Rod  Noise Connecting rod noise usually tends to give off a  light  knocking  or  pounding  sound.  The  sound is more noticeable when the engine is “floating” (not accelerating or decelerating) or as the throttle is eased off with the vehicle running at medium speed.  To  locate  a  noise  in  the  connecting  rod, 3-10