Auto Talk

Serpentine belts

One of the biggest changes to automobile engines in the last 20 years has been the change from multiple v-belts to a single flat-belt system, called a serpentine belt.

Belts are used to drive engine accessories such as the alternator, water pump, A/C condenser and power steering pump. The serpentine belt, so named because it winds like a snake around all the engine pulleys, has become the standard today for a variety of reasons, including the fact that one serpentine belt can do the work of several v-belts. The tradeoff is that with one belt running all the accessories, a failure means multiple problems: no battery charging, no coolant circulation to cool your engine, no power steering and other problems.

Advantages of a serpentine belt

Unlike a v-belt, a serpentine belt can drive pulleys from either side of the belt, allowing pulleys to be positioned closer together. In most cases, having all of the pulleys on one plane also allows belt tension to be maintained by a single spring-loaded tensioner. This generally eliminates the need for adjustment brackets and manual adjustments.

Having a single belt on the front of the engine, instead of a stack of belts, reduces the overall length of the engine and saves space. This is particularly important in front-wheel drive vehicles, which typically have transverse (sideways-mounted) engines and limited engine compartment space.

Serpentine belts also tend to last substantially longer than v-belts—sometimes two to three times longer. This is because there is less heat build-up, as they are wider and more flexible than a v-belt, with ribbed surfaces underneath to minimize slipping and allow better grip and pull.

Maintenance and replacement

As a rule, the maximum service life of a serpentine belt is five years or 60,000 miles. Newer serpentine belts made with superior materials can sometimes last up to ten years or 150,000 miles.

Despite the longer life, eventually heat, dirt, wear and old age will cause the demise of the belt. Regardless of age or mileage, any belt with extensive cracking, fraying or missing chunks of rubber should be replaced.

Oil-soaked or grease-covered belts also require replacement. If this is the reason for replacing a belt, make sure the source of oil or grease contamination is repaired first or it will continue to affect the new belt.

Belt failure can also result from the failure of one of the components being spun by the belt. To check whether this was a factor, repair facilities will spin all components while the belt is off.

Serpentine belt replacement is commonly done by a professional auto technician, due to the specialty tools required and the challenge of correctly installing the circuitous routing of the belts. Various idler pulleys or spring-loaded tensioners may also need replacement at the same time. Have the technician inspect coolant hoses, motor mounts, spark plug wires, and other wear items under the hood while your car is in for belt replacement.