SERVICE DIAGNOSIS—MECHANICAL
CONDITION POSSIBLE CAUSES CORRECTIONS
NOISY VALVES 1. High or low oil level in
crankcase.
1. Refer to Group 0, Lubrication and
Maintenance.
2. Thin or diluted oil. 2. Change oil and filter.
3. Low oil pressure. 3. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.
4. Dirt in lash adjusters. 4. Clean lash adjusters.
5. Bent push rods. 5. Replace as necessary.
6. Worn rocker arms. 6. Replace as necessary.
7. Worn tappets 7. Replace as necessary.
8. Worn valve guides. 8. Refer to Valve Service in this
section.
9. Excessive runout of valve seats
on valve faces.
9. Service valves and valve seats.
Refer to Valve Service in this
section.
CONNECTING ROD NOISE 1. Insufficient oil supply. 1. Refer to Group 0, Lubrication and
maintenance.
2. Low oil pressure. 2. Refer to Group 0, Lubrication and
maintenance.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Connecting rod journal
out-of-round.
5. Service or replace crankshaft.
6. Misaligned connecting rods. 6. Replace bent connecting rods.
MAIN BEARING NOISE 1. Insufficient oil supply. 1. Refer to Group 0, Lubrication and
maintenance.
2. Low oil pressure. 2. Refer to Group 0, Lubrication and
maintenance.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Excessive end play. 5. Check No. 3 main bearing for
wear on flanges.
6. Crankshaft journal out-of round. 6. Service or replace crankshaft.
7. Loose flywheel or torque
converter.
7. Tighten to correct torque
9 - 10 4.7L ENGINE DN
DIAGNOSIS AND TESTING (Continued)
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