Tensioners & Pulleys
Fits MERCEDES-BENZ CLA Coupe (C117) AMG CLA 45 4-matic (117.352)
(2015)

What are tensioners and pulleys?

Tensioners and pulleys are mechanical components on the engine that route and maintain the tension of a belt or a chain. It is important that any device that is powered by a belt or a chain have the correct tension level to ensure that the belt or chain does not slip or skip a tooth or link. This function is provided by the belt or chain tensioner. Pulleys help to route belts around the parts that require drive. This routing helps to provides grip/friction for the belt to drive the required device efficiently. Alternator pulleys provide a freewheel clutch which is specific to the type of alternator. A crankshaft pulley provides the drive required for the chain or belt. There are different types of tensioners.

These are:

• Hydraulic tensioner

• Mechanical tensioner

• Fixed tensioner

How do I choose the correct tensioner and pulleys?

There are different tensioners and pulleys required for your engine depending on the devices that require drive from the belt. Similarly there are different chain tensioners depending on the chain that is fitted to the vehicle. When making your choice to replace these parts it is best to obtain the part number directly from the item that you need to replace and compare it to parts that match that number.

If is not possible to get the part number here are some notes that may affect compatibility:

• With or without hydraulic or electric power steering

• With or without air conditioning

• Vehicle manufacture date (this is not the date the vehicle was registered but the date it was made)

• Engine number sequence (up to or after as specific number/letter

• VIN (chassis number) sequence (up to or after as specific number/letter)

What brand of tensioner or pulley should I choose?

Brands such as INA (Schaeffler) and Bosch manufacture parts for the original car brands so these are regarded as premium brands. There are other aftermarket brands such as Blue Print, SKF, Febi and and Borg & Beck that offer long warranties which helps give confidence in their parts are also a sign of quality. Your budget will likely play a large part in which brand you choose.

How can I tell my tensioner or pulley needs replacing?

There are so many symptoms of a faulty, failing or damaged tensioner or pulley. If you are not sure we would always recommend that a qualified mechanic diagnose the problem. Here are some issues that might indicate a faulty tensioner or pulley:

• Belt is loose causing it to slip or make a squealing sound

• Belt tensioner is easily moved or bounces off the belt

• Chain is loose / making a ticking or rattling sound

• Crankshaft or camshaft sensor codes

• Pulley does not spin freely or wobbles when in operation

• Squeaking or rattling noise from the tensioner that gets quicker the faster the engine is revved