A timing belt is a reinforced rubber belt which transfers the engine motion to the camshaft. The camshaft, in turn, operates the cylinder valves. The belt runs on a pulley from the crankshaft to the camshaft. (Quick note: not all cars use a rubber timing belt. Some vehicles use a timing chain.)

In short, the timing belt (or chain) keeps everything in sync by regulating the “timing” of the opening and closing of the valves with the up-and-down motion of the pistons. And with your engine operating at thousands of revolutions per minute, timing is critical, making this continuous loop of rubber or metal a crucial component of your engine.

Many car owners confuse a serpentine belt with the timing belt, but the two serve different purposes. In a nutshell, a timing belt keeps the camshaft and crankshaft in sync, regulating the “timing” of the opening and closing of the valves with the up-and-down motion of the pistons. It is also concealed from view by a cover that attaches to the engine block.

A serpentine belt, on the other hand, is so called because it’s long, snake-like movements transmit mechanical power to several very important engine accessories including the water pump, power steering pump, alternator, air and oil pumps, and the A/C compressor. You can see this belt when you lift the hood of your car.

The question remains: Why do I need to replace my serpentine belt? Because a bad or failing serpentine belt will cause your engine to overheat and eventually stop running. The good news is — as far as engine repairs go — serpentine belts are fairly inexpensive to replace.

The cost of replacing your timing belt varies from car to car, even location to location. Smaller passenger cars with smaller engines are generally less expensive than a larger vehicle with a bigger engine. Metropolitan areas usually mean higher costs, too.

Belts themselves aren’t that expensive. The real cost is in the labor, because a lot of parts need to be disassembled to get to the belt. Shopping around to get a few quotes is your best bet to get the best deal, but you can expect to pay anywhere from $367 to $585.

Have a timing chain instead of a timing belt? Lucky you, because they can actually last the lifetime of your car.

Although timing belts are critical, there’s no need to replace them regularly –unless explicitly recommended in your owner’s manual. Some automakers recommend changing a timing belt between 60,000 and 100,000, others don’t.

Many of today’s timing belts can go 100,000 miles or more without needing to be replaced. In fact, not all cars use a rubber timing belt. Some use a timing chain that can actually outlast the engine.

If your owner’s manual doesn’t have a recommended schedule, and you suspect something may be wrong, you can have a mechanic do a visual inspection, which includes removing the timing belt cover attached to the engine block. If your mechanic notices that your belt is cracked, frayed or worn down, then it’s time to replace your timing belt.

You don’t want to know. But if you must, it’s not good. There’s usually a lot of noise, and if you’re driving you won’t be for long. You’ll be stranded, and your engine will probably be damaged (metal components can actually break, hence all the noise). How much damage is anyone’s guess. Bottom line? Don’t let this happen.