The schedule for replacing a timing belt varies by manufacturer, with some saying it should be every 60,000 miles and others 100,000 miles or more. (Some engines have timing chains that shouldn’t require periodic replacement.) If the timing belt breaks, the engine can’t run. Worse, on some engines a broken belt can cause internal damage. A worn or stretched belt can cause engine vibrations, loss of power and other problems. Changing the timing belt requires removing a lot of other parts, adding to labor costs. If the timing belt drives the water pump, many mechanics recommend replacing the pump at the same time.