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DIAGNOSIS AND TESTING— ENGINE DIAGNOSIS - MECHANICAL 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 2. Thin or diluted oil 2. Change oil. (Refer to 9 - ENGINE/ 3. Low oil pressure 3. Check engine oil level. If ok, Perform 4. Dirt in tappets/lash adjusters 4. Clean/replace hydraulic tappets/lash 5. Bent push rod(s) 5. Install new push rods 6. Worn rocker arms 6. Inspect oil supply to rocker arms and 7. Worn tappets/lash adjusters 7. Install new hydraulic tappets/lash 8. Worn valve guides 8. Inspect all valve guides and replace 9. Excessive runout of valve seats or 9. Grind valves and seats CONNECTING ROD 1. Insufficient oil supply 1. Check engine oil level. 2. Low oil pressure 2. Check engine oil level. If ok, Perform 3. Thin or diluted oil 3. Change oil to correct viscosity. (Refer 4. Excessive connecting rod bearing Measure bearings for correct clearance 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 3. Thin or diluted oil 3. Change oil to correct viscosity. 9 - 68 ENGINE 3.9L AN ENGINE 3.9L (Continued) |