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Engine » 2.5L engine » Diagnosis and testing
Service diagnosis-mechanical

ENGINE MECHANICAL DIAGNOSIS CHART

CONDITION

POSSIBLE CAUSES

CORRECTION

NOISY VALVES/LIFTERS
  1. High or low oil level in crankcase
  2.  Thin or diluted oil
  3.  Low oil pressure
  4. Dirt in tappets/lash adjusters
  5.  Bent push rod(s)
  6.  Worn rocker arms and replace worn arms as needed
  7.  Worn tappets/lash adjusters
  8.  Worn valve guides replace as necessary
  9.  Excessive runout of valve seats or valve faces
  1. Check for correct oil level. Adjust oil level by draining or adding as needed
  2.  Change oil (Refer to Engine Oil Service in this group)
  3.  Check engine oil level. If ok, Perform oil pressure test. Refer to this group for engine oil pressure test/specifications
  4.  Clean/replace hydraulic tappets/lash adjusters
  5.  Install new push rods
  6. Inspect oil supply to rocker arms
  7. Install new hydraulic tappets/lash adjusters
  8. Inspect all valve guides and
  9.  Grind valves and seats
CONNECTING ROD NOISE
  1. Insufficient oil supply
  2.  Low oil pressure
  3.  Thin or diluted oil
  4.  Excessive connecting rod bearing clearance
  5.  Connecting rod journal out of round
  6.  Misaligned connecting rods
  1.  Check engine oil level. (Refer to group 0, Lubrication and Maintenance)
  2. Check engine oil level. If ok, Perform oil pressure test. Refer to this group for engine oil pressure test/specifications
  3. Change oil to correct viscosity. Refer to this group for correct procedure/engine oil specifications
  4. Measure bearings for correct clearance with plasti-gage. Repair as necessary
  5.  Replace crankshaft or grind journals
  6. Replace bent connecting rods
MAIN BEARING NOISE
  1. Insufficient oil supply
  2.  Low oil pressure
  3.  Thin or diluted oil
  4.  Excessive main bearing clearance
  5.  Excessive end play
  6.  Crankshaft main journal out of round or worn
  7.  Loose flywheel or torque converter
  1.  Check engine oil level. (Refer to group 0, Lubrication and Maintenance)
  2.  Check engine oil level. If ok, Perform oil pressure test. Refer to this group for engine oil pressure test/specifications
  3.  Change oil to correct viscosity. Refer to this group for correct procedure/engine oil specifications
  4.  Measure bearings for correct clearance. Repair as necessary
  5. Check crankshaft thrust bearing for excessive wear on flanges
  6.  Grind journals or replace crankshaft
  7.  Inspect crankshaft, flexplate/ flywheel and bolts for damage. Tighten to correct torque
LOW OIL PRESSURE
  1. Low oil level
  2.  Faulty oil pressure sending unit
  3.  Clogged oil filter
  4.  Worn oil pump
  5.  Thin or diluted oil
  6.  Excessive bearing clearance
  7.  Oil pump relief valve stuck
  8.  Oil pump suction tube loose, broken, bent or clogged
  9.  Oil pump cover warped or cracked
  1.   Check oil level and fill if necessary
  2.  Install new sending unit
  3.  Install new oil filter
  4.  Replace worn gears or oil pump assy
  5.  Change oil to correct viscosity. Refer to this group for correct procedure/engine oil specifications
  6.  Measure bearings for correct clearance
  7.  Remove valve to inspect, clean and reinstall
  8.  Inspect suction tube and clean or replace if necessary
  9.  Install new oil pump
OIL LEAKS
  1. Misaligned or deteriorated gaskets
  2.  Loose fastener, broken or porous metal part
  3.  Front or rear crankshaft oil seal leaking
  4.  Leaking oil gallery plug or cup plug
  1.  Replace gasket
  2. Tighten, repair or replace the part
  3.  Replace seal
  4.  Remove and reseal threaded plug. Replace cup style plug
EXCESSIVE OIL CONSUMPTION OR SPARK PLUGS OIL FOULED
  1. PCV System malfunction
  2.  Defective valve stem seal(s)
  3.  Worn or broken piston rings
  4.  Scuffed pistons/cylinder walls
  5.  Carbon in oil control ring groove
  6.  Worn valve guides
  7.  Piston rings fitted too tightly in grooves
  1.  Refer to group 25, Emission Control System for correct operation
  2.  Repair or replace seal(s)
  3.  Hone cylinder bores. Install new rings
  4.  Hone cylinder bores and replace pistons as required
  5.  Remove rings and de-carbon piston
  6. Inspect/replace valve guides as necessary
  7.  Remove rings and check ring end gap and side clearance. Replace if necessary
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