Timing belts came into vogue in the 1980s as a less expensive and quieter way to drive the camshafts on overhead-cam engines. The only downside to a timing belt, as you may have discovered, is that they have to be replaced at certain mileage intervals—intervals which are much shorter than the replacement intervals for chain-driven systems. And the consequences of not replacing a BMW Timing Belt aren’t something to blow off: You could be looking at a top-end rebuild at the least, and a new engine at the worst.

Today’s modern engines use such tight tolerances that the valves and the pistons have to be timed perfectly to prevent damage. The problem is that when a BMW timing belt breaks, the valves stop moving suddenly. The pistons, on the other hand, continue moving up and down. When the pistons meet the valves, bad things happen, so be certain to follow the manufacturer’s recommended BMW timing belt replacement interval.