The timing belt is one of the most overlooked parts of a vehicle. Because of that, thousands of cars break down each year because of old and worn out timing belts. A timing belt will wear down over time and have to be replaced every 60,000 to 100,000 miles. With a worn-down timing belt, your vehicle will experience engine vibration, misfires, and overall sluggish performance. If left untreated, a worn timing belt can break and lead to total engine failure.