CONTENTS
SOUNDS
UNDERHOOD
RHYTHMIC

DEEP, HEAVY, THUDDING SOUND

CONDITION(S)

• DEEP, HEAVY, THUDDING SOUND DULL IN PITCH (MAIN BEARING KNOCK)
• NOISE MORE PRONOUNCED WHEN ENGINE IS UNDER LOAD OR CAR IS ACCELERATING
• DEEP KNOCK IS ONLY HEARD UPON ENGAGING OR DISENGAGING THE CLUTCH

POTENTIAL CAUSE(S)

CHECK THESE FIRST:

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

2. WORN CRANKSHAFT JOURNAL OR BEARING
Have crankshaft journal or bearing professionally replaced.

3. OUT-OF-ROUND CRANKSHAFT
Have crankshaft professionally replaced.

CHECK THESE NEXT:

4. LOOSE FLYWHEEL
Have flywheel professionally tightened.

5. DIRT BEHIND CONNECTING ROD BEARINGS
Have connecting rod bearings professionally replaced.

CHECK THESE LAST:

6. CLOGGED OIL GALLERIES
Remove engine sludge.

7. DAMAGED OR MISALIGNED COOLING FAN
Have cooling fan professionally serviced.

CONTENTS
ENGINE SPUTTERS
NOISY PISTON RINGS