Engine Diagnosis - Mechanical

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ENGINE MECHANICAL DIAGNOSIS CHART

CONDITION	POSSIBLE CAUSES	CORRECTION
NOISY VALVES/LIFTERS	1. High or low oil level in crankcase.	1. Check for correct oil level. Adjust oil level by draining or adding as needed.
	2. Thin or diluted oil.	2. Change oil. See Engine/Lubrication/OIL - Standard Procedure .
	3. Low oil pressure.	3. Check engine oil level. If OK, Perform oil pressure test. See Engine/Lubrication - Diagnosis and Testing .
	4. Dirt in tappets/lash adjusters.	4. Clean/replace hydraulic tappets/lash adjusters.
	5. Bent push rod(s).	5. Install new push rods.
	6. Worn rocker arms.	6. Inspect oil supply to rocker arms and replace worn arms as needed.
	7. Worn tappets/lash adjusters.	7. Install new hydraulic tappets/lash adjusters.
	8. Worn valve guides.	8. Inspect all valve guides and replace as necessary.
	9. Excessive runout of valve seats or valve faces.	9. Grind valves and seats.
CONNECTING ROD NOISE	1. Insufficient oil supply.	1. Check engine oil level.
	2. Low oil pressure.	2. Check engine oil level. If OK, Perform oil pressure test. See Engine/Lubrication - Diagnosis and Testing .
	3. Thin or diluted oil.	3. Change oil to correct viscosity. See Engine/Lubrication/OIL - Standard Procedure .
	4. Excessive connecting rod bearing clearance.	4. Measure bearings for correct clearance with plasti-gage. Repair as necessary.
	5. Connecting rod journal out of round.	5. Replace crankshaft or grind journals.
	6. Misaligned connecting rods.	6. Replace bent connecting rods.
MAIN BEARING NOISE	1. Insufficient oil supply.	1. Check engine oil level.
	2. Low oil pressure.	2. Check engine oil level. If OK, Perform oil pressure test. See Engine/Lubrication - Diagnosis and Testing .
	3. Thin or diluted oil.	3. Change oil to correct viscosity.
	4. Excessive main bearing clearance.	4. Measure bearings for correct clearance. Repair as necessary.
	5. Excessive end play.	5. Check crankshaft thrust bearing for excessive wear on flanges.
	6. Crankshaft main journal out of round or worn.	6. Grind journals or replace crankshaft.
	7. Loose flywheel or torque converter.	7. Inspect crankshaft, flexplate/flywheel and bolts for damage. Tighten to correct torque.
LOW OIL PRESSURE	1. Low oil level.	1. Check oil level and fill if necessary.
	2. Faulty oil pressure sending unit.	2. Install new sending unit.
	3. Clogged oil filter.	3. Install new oil filter.
	4. Worn oil pump.	4. Replace oil pump assembly.
	5. Thin or diluted oil.	5. Change oil to correct viscosity.
	6. Excessive bearing clearance.	6. Measure bearings for correct clearance.
	7. Oil pump relief valve stuck.	7. Remove valve to inspect, clean and reinstall.
	8. Oil pickup tube loose, broken, bent or clogged.	8. Inspect oil pickup tube and pump, and clean or replace if necessary.
	9. Oil pump cover warped or cracked.	9. Install new oil pump.
	10. Faulty or missing piston cooling jets.	10. Replace piston cooling jets.
OIL LEAKS	1. Misaligned or deteriorated gaskets.	1. Replace gasket.
	2. Loose fastener or broken or porous metal part.	2. Tighten, repair or replace the part.
	3. Front or rear crankshaft oil seal leaking.	3. Replace seal.
	4. Leaking oil gallery plug or cup plug.	4. Remove and reseal threaded plug. Replace cup style plug.
EXCESSIVE OIL CONSUMPTION OR SPARK PLUGS OIL FOULED	1. CCV System malfunction.	1. Refer to EMISSIONS CONTROL .
	2. Defective valve stem seal(s).	2. Repair or replace seal(s).
	3. Worn or broken piston rings.	3. Hone cylinder bores. Install new rings.
	4. Scuffed pistons/cylinder walls.	4. Hone cylinder bores and replace pistons as required.
	5. Carbon in oil control ring groove.	5. Remove rings and de-carbon piston.
	6. Worn valve guides.	6. Inspect/replace valve guides as necessary.
	7. Piston rings fitted too tightly in grooves.	7. Remove rings and check ring end gap and side clearance. Replace if necessary.