The timing belt connects the crankshaft to the camshafts and controls when valves open and close. A loose or worn belt will cause ticking or rattling noises, poor engine performance and overheating, usually triggering the Check Engine light. If the timing belt breaks, the engine can’t run (and on some engines it will cause internal damage). Most engines have timing chains, which typically don’t require replacing. Timing belts, though, often have a recommended mileage for changing. On some engines, it’s as soon as 60,000 miles. On others it can be 100,000 or more.