Engine Diagnosis - Mechanical
WARNING: This page is about a different variant/trim than selected.
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 for engine oil pressure test/specifications | |
| 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 engine oil pressure test/specifications | |
| 3. Thin or diluted oil | 3. Change oil to correct viscosity. See Engine/Lubrication/OIL - Standard Procedure for correct procedure/engine oil specifications | |
| 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 | |
| OIL LEAKS | 1. Misaligned or deteriorated gaskets | 1. Replace gasket |
| 2. Loose fastener, 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 - Operation . |
| 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 |