4. Damaged slotted holes
Only for those types of torsional vibration dampers that have wear indicating tabs which allow checking the angular displacement of the rubber versus the pulley.
Appearance: Clear contact marks from the metal wear tabs in the slotted holes.
Cause: The metal wear tab is prevented from contacting the slotted hole until the rubber damping element has severely worn out. Once worn out, the tab repeatedly hits the slotted hole leaving clear contact marks.
Solution: Replace the torsional vibration damper.