- The harmonic balancer (vibration damper) is inspected for signs of wear in its center bore.
- Also inspect the rubber mounting for indications of twisting and deterioration.
- The outer ring can slip, causing an out of balance condition. Replace any harmonic balancer that has slipped.
- With the cylinder head removed and the piston at top dead center (TDC), make a visual comparison. Do the timing marks for TDC on the timing cover and damper appear to be accurate.
- Be sure the damper is the correct one for the vehicle. The wrong one can be worse than none at all.
- Sometimes a damper can become loose on the crank. Check the keyway for wear that can result from improper damper installation, the wrong size key, or a loose damper hub to crank fit.
- Be sure all pulleys are straight. A damaged pulley can force a crankshaft to bend during engine operation.
A heavy rumble or thumping noise that is most clearly heard when the vehicle is accelerated from an idle indicates a loose or worn harmonic balancer. Harmonic balancer noises are located at the front of the engine. If the harmonic balancer is worn or damaged, engine vibration may accompany the noise.