ENGINE DIAGNOSIS - MECHANICALCONDITIONPOSSIBLE CAUSESCORRECTION
NOISY VALVES1. High or low oil level in crankcase.1. Check and correct engine oil level.
2. Thin or diluted oil.2. Change oil to correct viscosity.
3. Thick oil3. (a) Change engine oil and filter.
(b) Run engine to operating temperature.
(c) Change engine oil and filter again.
4. Low oil pressure.4. Check and correct engine oil pressure problem.
5. Dirt in hydraulic lifters/lash adjusters.5. Replace hydraulic lifters/lash adjusters.
6. Worn rocker arms.6. Inspect oil supply to rocker arms.
7. Worn hydraulic lifters/lash adjusters.7. Replace hydraulic lifters/lash adjusters.
8. Worn valve guides.8. Replace cylinder head assembly.
9. Excessive runout of valve seats on valve faces.9. Grind valve seats and valves.
CONNECTING ROD NOISE1. Insufficient oil supply.1. Check engine oil level.
2. Low oil pressure.2. Check engine oil level. Inspect oil pump relief valve and spring.
3. Thin or diluted oil.3. Change oil to correct viscosity.
4. Thick oil4. (a) Change engine oil and filter.
(b) Run engine to operating temperature.
(c) Change engine oil and filter again.
5. Excessive bearing clearance.5. Measure bearings for correct clearance. Repair as necessary.
6. Connecting rod journal out-of-round.6. Replace crankshaft or grind surface.
7. Misaligned connecting rods. 7. Replace bent connecting rods.
MAIN BEARING NOISE1. Insufficient oil supply.1. Check engine oil level.
2. Low oil pressure.2. Check engine oil level. Inspect oil pump relief valve and spring.
3. Thin or diluted oil.3. Change oil to correct viscosity.
4. Thick oil4. (a) Change engine oil and filter.
(b) Run engine to operating temperature.
(c) Change engine oil and filter again.
5. Excessive bearing clearance.5. Measure bearings for correct clearance. Repair as necessary.
6. Excessive end play.6. Check thrust bearing for wear on flanges.
7. Crankshaft journal out-of-round or worn.7. Replace crankshaft or grind journals.
8. Loose flywheel or torque converter.8. Tighten to correct torque.
OIL PRESSURE DROP1. Low oil level.1. Check engine oil level.
2. Faulty oil pressure sensor/switch.2. Replace oil pressure sensor/switch.
3. Low oil pressure.3. Check oil pressure sensor/switch and main bearing oil clearance.
4. Clogged oil filter.4. Install new oil filter.
5. Worn parts in oil pump.5. Replace worn parts or pump.
6. Thin or diluted oil.6. Change oil to correct viscosity.
7. Oil pump relief valve stuck.7. Remove valve and inspect, clean, or replace.
8. Oil pump suction tube loose.8. Remove oil pan and install new tube or clean, if necessary.
9. Oil pump cover warped or cracked. 9. Install new oil pump.
10. Excessive bearing clearance.10. Measure bearings for correct clearance.
OIL LEAKS1. Misaligned or deteriorated gaskets.1. Replace gasket(s).
2. Loose fastener, broken or porous metal part.2. Tighten, repair or replace the part.
3. Misaligned or deteriorated cup or threaded plug.3. Replace as necessary.
OIL CONSUMPTION OR SPARK PLUGS FOULED1. PCV system malfunction.1. Check system and repair as necessary. (Refer to 25 - EMISSIONS CONTROL/EVAPORATIVE EMISSIONS/PCV VALVE - DIAGNOSIS AND TESTING)
2. Worn, scuffed or broken rings.2. Hone cylinder bores. Install new rings.
3. Carbon in oil ring slots.3. Install new rings.
4. Rings fitted too tightly in grooves.4. Remove rings and check grooves. If groove is not proper width, replace piston.
5. Worn valve guide(s).5. Replace cylinder head assembly.
6. Valve stem seal(s) worn or damaged.6. Replace seal(s).