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Your V-ribbed belt (poly v-belt) worn out? » Read more about common malfunctions • Repair • Replacement manual
More power, less squeak with the serpentine belt
Who still remembers the ghastly sound of a car with a slack V-belt driving by? The reason why this sound has all but disappeared from the public notion is the serpentine belt. This type of belt (poly-v or v-ribbed) has almost completely replaced the traditional V-belt. Nevertheless, noise reduction was not the real reason for the re-design of the drive belt.
Higher performance by the same generator
The reason for replacing the V-belt by the serpentine belt lies in higher user expectations. The modern car is equipped with considerably more electronics than used to be the case. Seat heating, air conditioning, safety and comfort systems, sensors, powerful audio systems etc. demand a lot more from the generator than the old 12 V dynamos would be able to supply. Installing larger generators would be one solution for enhancing the electricity supply in the car. This would however become disproportionally expensive. Instead, the available generator is run at a higher speed. This has however a significant disadvantage: the bearing wears quicker when the generator is driven by a traditional V-belt.
Diminish wear by freewheeling
To get more performance out of the same generator and in the meantime keep the wear of the bearings under control, manufacturers use a trick: in modern cars the generator has a flywheel. This means it can only be driven in one direction. When the engine is revving low, the freewheeling flywheel maintains the rotational energy until it has reached the new rpm. In a rigid connection between V-belt and generator, the generator speed was permanently reduced and subsequently enhanced. Freewheeling spares the bearings with less wear as a result.
Tensioning the serpentine belt
The belt must maintain tension for optimal drive of the flywheel generator. This applied to e V-belt as well. In case of a rigid connection between drive and generator, the belt tension was adjusted directly on the generator. The flywheel requires an external tensioner pulley, maintaining flexible tension. Flywheel and tensioner pulley in their turn need a broad contact surface– and only for this reason the narrow V-belt had to be replaced by the considerably broader serpentine belt.
Same performance, larger surface
The serpentine belt is a flat belt strengthened by longitudinal ribs. The V-shaped ribs have the same function as on the traditional V-belt: they stabilise the belt and enhance the contact surface on the generator flywheel and the drive wheel of the engine. In many cars the serpentine belt additionally drives the water pump, causing a lot of stress for the component.
Replacement of the serpentine belt
The replacement of a serpentine belt is not as simple as it used to be. Expertise on the functioning of the tensioner is required. Modern branded belts are very durable. They are replaced simultaneously with the flywheel and tensioner on occasion of a service interval. This is not as cheap as a V-belt replacement used to be, although it re-establishes full functionality of the car for the coming maintenance intervals in one go. If the belt breaks down prematurely, this is probably the result of mechanical damage. This should be most certainly checked. Often rodents are responsible for prematurely malfunctioning serpentine belts. The belt itself costs only between 5 and 20 euro (£4.50 - £18) and with some dexterity can be replaced in a couple of minutes. Due to the high strain, branded quality is essential. Only this ensures the desired security for long and relaxed driving.