The timing belt runs between the top and bottom half of the engine and keeps the crank and camshafts timed properly. It is essential that this timing is not disturbed. Cars older than 1999 and newer Audi are subject to timing belts, whereas most newer cars are now on timing chains. There are typo types of engine timing configurations, interference and non-interference. In interference engines the timing belt is essential to prevent catastrophic engine damage. A snapped timing belt in such an engine can lead to thousands of dollars in repairs. In non-interference engines a snapped timing belt only means the belt needs to replaced.