Every vehicle has an accessory belt to drive the air conditioning compressor or alternator. Sometimes, the accessory belt also runs the power steering and water pumps, but that isn’t always the case. Usually, the belt is mounted externally so that you can see it at the front of the engine. Of course, that’s only on a transverse mount for front-wheel-drive vehicles. The serpentine belt usually slithers around the various pulleys to make the different components run. If you notice cracks, stretching, or fraying, it should be replaced soon.
Some cars also use a timing belt that’s hidden from plain sight but connects the cylinder head on the top of the engine with the crankshaft at the bottom. It’s designed to control when the valves get opened or closed. Most modern engines use a timing chain rather than a belt. The timing chain is a lifetime part, so it doesn’t require replacement. The timing belt does need to be replaced. Most manufacturer maintenance schedules don’t call for replacement until 150,000 miles.
If the Belt Breaks
If your timing or accessory belt breaks, your vehicle isn’t going to run much longer. If the timing belt does breaks, the engine automatically shuts off, and it can’t be restarted. With the serpentine/accessory belt, you can sometimes restart the car after it breaks, but you can’t get far because it powers the alternator. Without your alternator running at full capacity, you rely solely on battery power to move you; when that is gone, there’s nothing else you can do but call for a tow truck.
When to Inspect
Serpentine belts can sometimes be designed to last over 100,000 miles, but it does vary by manufacturer. Most maintenance schedules tell you when to have the belts inspected and what belts you have on the vehicle. However, they can vary widely by manufacturer. For example, Hyundai claims that you should have the belts inspected after 60,000 miles or six years and then every 15,000 miles or two years afterward. Some brands just say to check the belts every 40,000 miles (Volkswagen), and Ford tells consumers to wait until 100,000 miles.
Replacement costs for a serpentine belt can vary widely. If you aren’t mechanically inclined, you’re likely to spend more for labor to have a reputable technician put the part on correctly and safely. It’s always best to get the belts inspected before it’s recommended; you shouldn’t do it too far in advance, but you should do it a few thousand miles before its recommended; that way, you can determine if it needs to be replaced and can shop around for the best deal on parts and labor.
The serpentine belt may give warning signs that it needs to be replaced, including rattling noises from a tensioner or pulley or squealing sounds when you accelerate or start up the engine.
The timing belt is much more involved and more expensive to replace. Plus, if the belt breaks, the pistons might continue to move and hit or bend valves in the process, which can add to repair costs. Therefore, it is essential that you get the timing belt replaced before it breaks. However, it’s not visible when you peer under the hood, so you can’t check it easily. A mechanic has to remove all the accessory drive belts and engine cover just to see it. Then, they have to reassemble it all. They are likely to charge a fee, at which many people balk. Therefore, it’s best to pay attention to the replacement schedule of the manufacturer. These can vary based on the brand, but you should be okay if you follow your owner’s manual.