CONDITION
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POSSIBLE CAUSES
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CORRECTION
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NOISY VALVES
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1. High or low oil level in crankcase.
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1. Check and correct engine oil level.
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2. Thin or diluted oil.
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2. Change oil to correct viscosity.
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3. Thick oil
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3. (a) Change engine oil and filter.
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(b) Run engine to operating temperature.
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(c) Change engine oil and filter again.
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4. Low oil pressure.
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4. Check and correct engine oil pressure problem.
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5. Dirt in hydraulic lifters/lash adjusters.
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5. Replace hydraulic lifters/lash adjusters.
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6. Worn rocker arms.
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6. Inspect oil supply to rocker arms.
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7. Worn hydraulic lifters/lash adjusters.
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7. Replace hydraulic lifters/lash adjusters.
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8. Worn valve guides.
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8. Replace cylinder head assembly.
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9. Excessive runout of valve seats on valve faces.
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9. Grind valve seats and valves.
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CONNECTING ROD NOISE
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1. Insufficient oil supply.
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1. Check engine oil level.
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2. Low oil pressure.
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2. Check engine oil level. Inspect oil pump relief valve and spring.
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3. Thin or diluted oil.
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3. Change oil to correct viscosity.
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4. Thick oil
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4. (a) Change engine oil and filter.
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(b) Run engine to operating temperature.
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(c) Change engine oil and filter again.
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5. Excessive bearing clearance.
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5. Measure bearings for correct clearance. Repair as necessary.
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6. Connecting rod journal out-of-round.
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6. Replace crankshaft or grind surface.
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7. Misaligned connecting rods.
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7. Replace bent connecting rods.
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MAIN BEARING NOISE
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1. Insufficient oil supply.
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1. Check engine oil level.
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2. Low oil pressure.
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2. Check engine oil level. Inspect oil pump relief valve and spring.
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3. Thin or diluted oil.
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3. Change oil to correct viscosity.
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4. Thick oil
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4. (a) Change engine oil and filter.
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(b) Run engine to operating temperature.
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(c) Change engine oil and filter again.
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5. Excessive bearing clearance.
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5. Measure bearings for correct clearance. Repair as necessary.
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6. Excessive end play.
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6. Check thrust bearing for wear on flanges.
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7. Crankshaft journal out-of-round or worn.
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7. Replace crankshaft or grind journals.
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8. Loose flywheel or torque converter.
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8. Tighten to correct torque.
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OIL PRESSURE DROP
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1. Low oil level.
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1. Check engine oil level.
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2. Faulty oil pressure sensor/switch.
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2. Replace oil pressure sensor/switch.
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3. Low oil pressure.
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3. Check oil pressure sensor/switch and main bearing oil clearance.
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4. Clogged oil filter.
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4. Install new oil filter.
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5. Worn parts in oil pump.
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5. Replace worn parts or pump.
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6. Thin or diluted oil.
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6. Change oil to correct viscosity.
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7. Oil pump relief valve stuck.
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7. Remove valve and inspect, clean, or replace.
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8. Oil pump suction tube loose.
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8. Remove oil pan and install new tube or clean, if necessary.
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9. Oil pump cover warped or cracked.
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9. Install new oil pump.
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10. Excessive bearing clearance.
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10. Measure bearings for correct clearance.
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OIL LEAKS
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1. Misaligned or deteriorated gaskets.
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1. Replace gasket(s).
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2. Loose fastener, broken or porous metal part.
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2. Tighten, repair or replace the part.
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3. Misaligned or deteriorated cup or threaded plug.
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3. Replace as necessary.
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OIL CONSUMPTION OR SPARK PLUGS FOULED
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1. PCV system malfunction.
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1. Check system and repair as necessary. (Refer to 25 - EMISSIONS CONTROL/EVAPORATIVE EMISSIONS/PCV VALVE - DIAGNOSIS AND TESTING)
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2. Worn, scuffed or broken rings.
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2. Hone cylinder bores. Install new rings.
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3. Carbon in oil ring slots.
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3. Install new rings.
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4. Rings fitted too tightly in grooves.
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4. Remove rings and check grooves. If groove is not proper width, replace piston.
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5. Worn valve guide(s).
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5. Replace cylinder head assembly.
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6. Valve stem seal(s) worn or damaged.
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6. Replace seal(s).
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