CONTENTS
SOUNDS
UNDERHOOD
RHYTHMIC

LIGHT, TAPPING NOISE

CONDITION(S)

• NOISE SPEEDS UP OR SLOWS DOWN WITH ENGINE SPEED
• NOISE (VALVE TRAIN CLATTER) HEARD LOUDEST FROM THE TOP OF THE ENGINE
• ACCOMPANIED BY NOTICEABLE ENGINE VIBRATION AT IDLE THAT INCREASES UNDER LOAD
• ACCOMPANIED BY MUFFLED BACKFIRE THAT OCCURS UPON ACCELERATION
• ENGINE IS OVERHEAD CAMSHAFT DESIGN
• SOUND IS FROM FRONT OF ENGINE
• ACCOMPANIED BY EXHAUST ODOR AND GRAYISH-WHITE DEPOSITS ARE NEAR EXHAUST SYSTEM CONNECTIONS

POTENTIAL CAUSE(S)

CHECK THESE FIRST:

1. WORN, STUCK (DIRTY), OR DEFECTIVE HYDRAULIC VALVE LIFTERS
Have hydraulic valve lifters professionally serviced.

2. EXCESSIVE VALVE LASH ON MECHANICAL LIFTERS
Have valve lash on mechanical lifters professionally adjusted.

3. WORN VALVE GUIDE OR STEM
Have valve or valve guide professionally replaced.

4. LOW OIL PRESSURE
Have cause of low oil pressure professionally corrected.

CHECK THESE NEXT:

5. CONTAMINATED OR DIRTY OIL
Change oil and filter.

6. WORN ROCKER ARMS AND/OR SHAFTS
Have rocker arms and/or shafts professionally replaced.

7. CLOGGED OIL GALLERIES
Remove engine sludge.

8. LOW OIL LEVEL
Add oil if necessary.

CHECK THESE LAST:

9. BROKEN VALVE SPRING
Have valve spring professionally replaced.

10. WORN OR BENT PUSH RODS
Have push rods professionally replaced.

11. THIN OR DILUTED (CONTAMINATED) OIL
Change oil and filter; use correct grade of oil.
Alter driving habits.

12. EXCESSIVE RUNOUT OF VALVES OR VALVE SEATS
Have valves or valve seats professionally serviced.

CONTENTS
ENGINE KNOCKS OR PINGS
HALLOW, RAPPING SOUND