Your Complete Guide to Vehicle Engine Belts (2024)

A serpentine belt is a rubber engine belt that drives several of your car's key accessories, including the alternator, power steering pump, A/C compressor, and in some cases, the water pump. It is part of an asynchronous drive system powered by the engine's crankshaft and operated by a combination of pulleys and a tensioner.

A single serpentine belt is a modern replacement for the drive belts (also called V-belts) found in older cars, which consisted of multiple thicker and less flexible belts to operate the same accessories.

Serpentine belts are made from high-quality rubber or neoprene, though belts made from more durable Ethylene Propylene Diene Monomer (EPDM) — a type of synthetic rubber — are becoming increasingly common.

Serpentine belts are often constructed with a smooth side and a ribbed side that features four to six grooves running along the belt's length. These grooves are designed to mesh with the pulleys to increase traction and prevent slippage while running.

The main advantage of modern serpentine belts is their simplicity. The single, flatter serpentine belt allows for a more compact engine bay design and means car owners only have to worry about replacing one belt as opposed to the multiple V-belts found in earlier car models.

At the same time, however, a single belt poses a disadvantage in that all of the accessories powered by the belt stop functioning if it becomes damaged or breaks.

A general rule of thumb is to replace the serpentine belt every 60,000 miles or roughly every five years. Higher quality belt material, such as EPDM belts, can last up to 100,000 miles before needing replacement. Either way, it's a good idea to regularly inspect your engine belts for wear and perform preventative maintenance as needed.

Keep in mind that inspecting your serpentine belt also means checking the tensioner and pulleys. These components are part of the same system and are just as important as the belt itself.

Often, the tensioner, which keeps the belt taut, and idler pulleys, which keep it properly aligned, suffer from similar wear and tear. It's generally a good idea to replace the tensioner as well when you start noticing serpentine belt problems such as cracks or squealing.

You do not want to be in a moving car when the serpentine belt breaks. A broken serpentine belt will cause the power steering pump to stop working, making it significantly harder to steer your vehicle to a stop.

In the case of cars with serpentine belts that operate the water pump, it is also possible for the engine to overheat. This is because the water pump is responsible for pumping coolant to the engine and managing its heat output.

Additionally, a broken serpentine belt can make it hard (or impossible) to start your car, as the alternator will not generate electricity. Your A/C compressor will also lose its ability to circulate refrigerant, preventing cool air from flowing into the cabin. The best plan to avoid these issues is to perform preventative maintenance and inspect your serpentine belt system at regular intervals.

A timing belt is a synthetic rubber engine belt responsible for keeping an engine's crankshaft and camshaft in sync. It is part of a synchronous drive system, meaning each part of the system must be perfectly timed with the others to function properly. The timing belt is often also responsible for operating the water pump, though the serpentine belt takes over this function in some cars.

The timing belt is vitally important to the operation of a car's engine. The belt is constructed with dense rubber “teeth” (raised bars that run perpendicular to the length of the belt) that mesh with a pulleys system and a tensioner that keeps the belt taut around the pulleys.

The belt's rotation around the pulleys spins the crankshaft and camshaft at precise, alternating intervals. For a four-stroke engine to successfully cycle between intake, compression, combustion, and exhaust phases, the pistons on the crankshaft and the engine valves on the camshaft must alternate in time.

Though there are some cars on the road that still use timing belts, the timing belt has become quite an antiquated technology. Many manufacturers have replaced timing belts with timing chains on modern vehicles. Timing chains are responsible for most, if not all, of the same functions of a timing belt. Additionally, a timing chain is more durable than the rubber in a timing belt and can generally last as long as the vehicle's lifespan.

Similar to serpentine belts, timing belts are not meant to last the lifetime of your vehicle. They should be inspected regularly after 60,000 miles of use and replaced if any wear signs are present.

In newer cars, timing belts may last up to 100,000 miles before needing to be replaced. Still, best practice is to have the belt's condition periodically checked and get preventative maintenance to avoid belt failure on the road.

If your timing belt breaks, you may suffer serious engine damage. When the crankshaft’'s pistons are out of sync with the camshaft's engine valves, they can collide and cause serious damage. Bent valves and broken pistons are altogether a much more complicated and expensive repair to make than simply replacing the timing belt when it shows signs of wear.

However, it's worth noting that such damage is only possible on vehicles with an interference engine — meaning the engine's pistons and valves operate in overlapping space (thus creating the possibility for collision).

For cars with a non-interference engine, the risk of engine damage is minimal as the pistons and valves have no chance of colliding. Either way, a broken timing belt can leave you stranded by the side of the road, regardless of your engine type.

Modern cars have two types of engine belts: a serpentine belt and a timing belt. Serpentine belts operate essential accessories in your car, including the alternator, power steering pump, and A/C compressor. On the other hand, timing belts drive the synchronized movement of the crankshaft and camshaft, which are critical to powering the engine.

Both serpentine and timing belts have similar lifespans: they should be routinely inspected for wear after passing 60,000 miles of use and replaced before reaching 100,000 miles, if not sooner. An unexpected belt break while driving can cause extensive damage to other parts. That's why it's always better to proactively replace engine belts at the first sign of wear.

Engine belts can be replaced relatively easily with a few basic tools. Often, the trickiest part is remembering the path of the belt — consider drawing it out, taking a picture of how the belts are set before removal, or checking your owner's manual.

Keep in mind that timing belts are usually more difficult to access due to the cover over the belt assembly. Most importantly, serpentine and timing belts come in varying sizes according to your INFINITI's model. Make sure you have the right size for your INFINITI before attempting to replace either belt.