Drivers should replace timing belts on their vehicles every 50,000 to 100,000 miles. A vehicle's manual provides more specific information on when to replace the belt.
Some timing belts continue to perform past 100,000 miles, and some fail before the recommended replacement time. Replace the belt as soon as possible after purchasing a used vehicle with an unknown history or when fluids have leaked onto the belt, recommends The Car Connection. It is much more expensive to repair damage from a belt that breaks during operation than to replace it as prevention, and it is nearly impossible to determine when a belt is likely to break.