In a typical timing belt drive configuration, the belt is wrapped around one or more pulleys that always keep it taut and aligned. In today’s article we learn a little more about one of these components, the tensioner pulley, and its importance in the transmission of our vehicle.

The timing system is essential to maintaining the good performance of a vehicle. In it, the responsible for achieving a precise transmission and for achieving a proper and constant tension in the belt is none other than the tensioning pulley.

Among its main functions we find:

  • Increases the angle embraced in belt drives.
  • Gives tension to the belt and transfers the driving force of the crankshaft.
  • Compensates for the elongation of the strap, typical over time.
  • Allow for shorter wheelbases.
  • Prevents belt slippage.


Pulley Design


A pulley is a seemingly simple component, but how many types are there?

Its rolling surface can be both smooth and profiled and its basic components include a pulley in which a rigid radial bearing with one or two rows of balls is integrated. Inside it we find the inner ring and the outer ring, the retainer, the grease, and the seal.

Among the different types of tensioner pulleys, we differentiate between those that are fixed or automatic, being the last one capable of compensating their status regardless of the temperature reached or the load changes on the belt.


When to replace a Pulley?


As the belt, the pulley is a maintenance item, which means that it does wear out over time; mainly due to its free spinning activity. 

Generally, pulleys will last longer than belts, so inspecting the pulleys and bearings through maintenance is key for best practice. In many cases and depending on the materials from which the pulleys are produced, It is becoming more and more common to carry out the complete maintenance of the primary transmission replacing all the components of the distribution subject to wear at once.

At Dolz we also always recommend replacing the water pump in this same operation for three reasons:

  1. Greater quality and safety of the service provided.
  2. Best fit together of all components from the start.
  3. Greater savings. Reduction to half of the visits to the workshop.


Learn more: Reasons to replace the timing belt and the water pump


Potential signs of malfunctioning


A fault in the distribution system can be fairly easily diagnosed if paying attention to a number of warning signals. 

Tips for detecting a worn pulley and the need to replace the full system:

  • If you can hear odd noises such as a squealing, grinding or screeching sound coming from your vehicle, this is likely caused by a seized or loose bearing in the pulley. 
  • If the noise coming from the vehicle’s engine sounds more like a chattering kind of noise, it is probably the pulley itself that is seized up or loose.
  • If you have the chance to look into the pulley and it shows a corroded surface, it means that it will probably cause premature wear on the belt.
  • If when spinning the pulley, it keeps spinning excessively (more than a few rotations), or it is not spinning at all, the pulley is not working properly. And sooner rather than later it will end up breaking down.

Replacing broken and worn pulleys is not an option. Pulleys should move freely but softly, and without wobbling or hesitation. Although the need for replacement will probably translate into noticeable noises coming from the vehicle, it is crucial to undertake periodical and preventive maintenance for best engine performance.


Keep reading: All you need to know about Dolz kits 


Dolz, your trusted manufacturer


With more than 80 years of history, Dolz is your trusted manufacturer and distributor. The Dolz Kits include all the components required for a professional repair, from the belt and pulleys to the necessary bolts and nuts.

If you are looking for a premium partner with quality products equivalent to OE, contact us or browse through our catalogues for an effortless buying experience!


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