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The Independent Automotive Aftermarket Federation

Pulley Failure and Diagnosis - Guidance from Corteco


Date: 06-Nov-2018

Similar to other components failing, the part that has failed is often condemned before the true cause of the failure is found. If the component that is replaced isn’t the cause of the failure, it is highly likely that the vehicle will return to the garage several times until the root cause is found. In this guide, we will take you through the causes and tips on how to avoid premature failures in the future.

Vibrations often arise as a result of aging components or poor quality vibration dampers. These vibrations don’t just affect driving comfort. Unwanted vibrations can spread throughout the vehicle and cause damage to the engine and other components.

Installation damages:
One of the biggest causes of failures occurs during the fitting stage, below explains the identifications and cause of installation damages.

If the pulley has been fitted with the incorrect tightening torque you will be able to see defect characteristics such as; discolouration or burning of the mounting sleeve, material abrasions in the installation area as well as the drill hole being deformed. All components come with a recommended torque, this should be checked before the parts are tightened.

Similarly, if the belt tension is too strong or the auxiliary equipment has failed the pulley will also fail. The cause is linked to the coupling having made contact with the flywheel rim. When removing the pulley you will be able to see visible abrasions in the Poly-V and residue from the belt in the ribs.

When removing a pulley from a vehicle and you see the hub is visibly broken then this has been caused by the wrong assembly tool being used or the chamber support coming in contact with the bearing surface. Checking all aspects of the installation from start to finish can ensure the hub remains intact and protected from damage.

Alternatively, if the centring pin is worn out, the failure will stem from a relative movement between the coupling and pulley causing the effloresce. This can also be due to a missing or wrong diamond wheel disc being fitted. 

Another way a pulley can fail is during the fitting process there has been an interruption with the assembly press or the friction bearing has been incorrectly pressed in. This can occur during the making and installation of the part with the vehicle. To ensure the pulley is correct when delivered to you, visually check all areas before installing.

Similarly, to other components, if the area is contaminated with oil it will stop the pulley from functioning correctly causing it to slip on the belt and leak additional vibrations into the engine and to surrounding components.

As mentioned earlier, finding residue from the belt in the pulley ribs narrows down the cause of failure to excessive belt tension. Checking this before the vehicle is released can prevent it from returning to the garage for another repair.

With relation to pulleys that are found to be damaged / discoloured when removed from a vehicle that has recently been repaired, you need to ensure that you are working with the correct tools and all bolts are replaced at the same time as the pulley.

If the pulley is removed and there are chips and damages, these were potentially there when it was fitted. A pulley needs to be handled with care to avoid damage and chips to all ribs, make sure to check this before installation.

Following the guidance in this article can save all parties time and money. The extensive OE manufacturing experience of the Freudenberg Group enables Corteco to offer vibration control components and repair kits in OEM quality for more than 27,500 types of vehicles. All products are designed to meet the highest quality standards and are manufactured using the latest production methods,  Corteco offer a lifetime warranty on these parts as we are confident these parts will not fail unless incorrect steps are taken during installation / handling of the product. 

For more information on pulleys or any components from our vibration control range head to: http://www.corteco.com/en/products/vibration-control/ 

Alternatively, for any additional information please contact service@corteco.co.uk

To download the leaflet, click on the link below:


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