Many car owners may wonder how often to replace a timing belt. The old rule was every 60,000 miles. As technology has improved, many manufacturers recommend intervals up to 100,000 miles. To be safe you should check what the vehicle’s manufacturer recommends and stay within that mileage. Faulty timing belt symptoms include a loss of power, loss of fuel economy, misfiring and engine vibration.You can face expensive repairs if the belt breaks. With regard to questions about how to check a timing belt, this is a job for a qualified repair shop.