Most drivers know that the drive belts can be the cause of poor accessory performance and noise, but what many don’t realize is that the pulleys that contact the belt can often be the underlying cause of these malfunctions. Modern serpentine belts are part of a sophisticated accessory drive system, and each part of that system must work properly in order for the accessories to deliver peak performance and quiet operation.

Featured Products

  • Dayco® GOLD Label™ No Slack™ Automatic Belt Tensioner Assembly
    (0 reviews)
    # sp6014
    GOLD Label™ No Slack™ Automatic Belt Tensioner Assembly by Dayco®. Constructed for heavy duty diesel engine accessory drive applications, this product handles the higher torque and power pulses exerted by diesel engines better...
    $68.95 - $95.74
  • Dayco® No Slack™ Automatic Belt Tensioner Assembly
    (0 reviews)
    # sp6016
    No Slack™ Automatic Belt Tensioner Assembly by Dayco®. Designed to maintain constant belt tension, this tensioner provides less variations in tension to prevent premature accessory bearing failure due to high belt tension, when a...
    $26.21 - $175.40
  • Melling® Engine Timing Belt Idler
    (0 reviews)
    # sp11984
    Engine Timing Belt Idler by Melling®. Melling timing belt tensioners are available as individual components only. Every Melling tensioner is designed and built to meet or exceed OEM requirements for the application. New tensioners...
    $28.86 - $122.33
  • ACDelco® GM Original Equipment™ Engine Crankshaft Pulley
    (0 reviews)
    # sp10354
    GM Original Equipment™ Engine Crankshaft Pulley by ACDelco®. Designed utilizing the latest technology, this GM Original Equipment Crankshaft Pulley by ACDelco features premium quality and will perform better than advertised....
    $33.51 - $145.47
  • Melling® Engine Timing Belt Tensioner
    (0 reviews)
    # sp11982
    Engine Timing Belt Tensioner by Melling®. Melling timing belt tensioners are available as individual components only. Every Melling tensioner is designed and built to meet or exceed OEM requirements for the application. New...
    $13.26 - $237.59
  • Dorman® A/C Compressor Bypass Pulley
    (5 reviews)
    # sp6557
    A/C Compressor Bypass Pulley by Dorman®. Now there’s an affordable, effective way to get your vehicle up and running after a seized A/C compressor renders it inoperable. Dorman’s A/C Compressor Bypass Pulley is installed in...
    $25.81 - $71.74
  • Beck Arnley® Timing Idler Pulley
    (0 reviews)
    # sp6523
    Timing Idler Pulley by Beck Arnley®. For one hundred years, Beck/Arnley has been providing premium OE quality parts for vehicles. Beginning with motorcycle parts in 1914 and transitioning to import vehicles in the 1950’s, brand...
    $21.82 - $67.66
  • ACDelco® Professional™ Idler Pulley
    (0 reviews)
    # sp11853
    Professional™ Idler Pulley by ACDelco®. The ACDelco Professional, premium aftermarket Idler Pulley is designed for use on automobiles and light duty trucks as a locked center tensioning pulley, an automatic belt tensioner pulley,...
    $17.00 - $54.14
  • URO Parts® Drive Belt Idler Pulley
    (0 reviews)
    # sp12893
    Drive Belt Idler Pulley by URO Parts®. Replace your worn out engine part with this superior engine component designed by URO to restore your vehicle's factory performance. Manufactured to meet the highest OE standards, this...
    $13.64 - $57.43
  • Gates® DriveAlign™ Premium OE Idler Pulley
    (0 reviews)
    # sp6077
    DriveAlign™ Premium OE Idler Pulley by Gates®. When you’re low on oil, coolant or some other fluid, you may be tempted to just run down to the local auto parts chain store. But before you waste your time and gas only to find...
    $14.41 - $81.36
  • Dayco® No Slack™ Belt Tensioner Pulley
    (1 reviews)
    # sp6017
    No Slack™ Belt Tensioner Pulley by Dayco®. Manufactured using sophisticated three dimensional computer aided design (CAD) and finite element analysis (FEA), this product ensures the optimal design and maximum structural integrity...
    $13.16 - $82.45
  • ACDelco® GM Original Equipment™ Drive Belt Idler Pulley
    (0 reviews)
    # sp11727
    GM Original Equipment™ Drive Belt Idler Pulley by ACDelco®. ACDelco GM Original Equipment Drive Belt Idler Pulleys are part of the accessory drive belt system on the front of your engine and are GM-recommended replacements for...
    $18.58 - $89.69
  • Gates® Timing Belt Tensioner Pulley
    (0 reviews)
    # sp6092
    Timing Belt Tensioner Pulley by Gates®. When you’re low on oil, coolant or some other fluid, you may be tempted to just run down to the local auto parts chain store. But before you waste your time and gas only to find high prices...
    $27.11 - $104.31
  • URO Parts® Drive Belt Tensioner
    (1 reviews)
    # sp12894
    Drive Belt Tensioner by URO Parts®. Replace your worn out engine part with this superior engine component designed by URO to restore your vehicle's factory performance. Manufactured to meet the highest OE standards, this reliable...
    $7.08 - $66.74
  • Gates® Timing Belt Tensioner
    (0 reviews)
    # sp6090
    Timing Belt Tensioner by Gates®. When you’re low on oil, coolant or some other fluid, you may be tempted to just run down to the local auto parts chain store. But before you waste your time and gas only to find high prices and...
    $22.27 - $143.98
  • Gates® Timing Idler
    (0 reviews)
    # sp4875
    Timing Idler by Gates®. When you’re low on oil, coolant or some other fluid, you may be tempted to just run down to the local auto parts chain store. But before you waste your time and gas only to find high prices and poor...
    $20.62 - $106.45
  • Hayden® Idler / Tensioner Pulley
    (0 reviews)
    # sp5688
    Idler / Tensioner Pulley by Hayden®. This part is designed to route the drive belt and keep it tight. If the pulley goes bad, it can cause problems with cooling, charging, steering, and climate control. Replace a faulty pulley with...
    $12.44 - $65.12
  • Continental® ContiTech™ Accessory Drive Belt Kit
    (4 reviews)
    # sp5984
    ContiTech™ Accessory Drive Belt Kit by Continental®. When replacing a worn out serpentine belt, it's a good practice to also replace the idlers and tensioners along with it to prevent uneven wear and the risk of failure in the...
    $38.61 - $361.48
  • ACDelco® Professional™ Automatic Belt Tensioner and Pulley Assembly
    (0 reviews)
    # sp11836
    Professional™ Automatic Belt Tensioner and Pulley Assembly by ACDelco®. The ACDelco Professional, premium aftermarket Automatic Belt Tensioner is designed for Accessory Belt Drive Systems (ABDS) that require an automatic belt...
    $35.07 - $191.50
  • Gates® Accessory Belt Drive Kit
    (0 reviews)
    # sp6076
    Accessory Belt Drive Kit by Gates®. When you’re low on oil, coolant or some other fluid, you may be tempted to just run down to the local auto parts chain store. But before you waste your time and gas only to find high prices and...
    $44.39 - $201.03
  • Auto Metal Direct® Crankshaft Pulley
    (0 reviews)
    # sp6503
    Crankshaft Pulley by Auto Metal Direct®. The restoration experts at Auto Metal Direct manufacture correct OE-quality replacement parts that will help you restore your vehicle to its original condition. Authentic look, precise fit,...
    $47.10 - $82.07


Featured Brands

In a typical serpentine belt accessory drive system there is a drive pulley that is part of or attached to the crankshaft mounted harmonic balancer, a pulley at each of the belt-driven accessories, a belt tensioner and one or more idler pulleys. The rubber ring between the hub and inertia ring on the harmonic balancer can fail and these components are discussed more in depth on our Harmonic Balancers product page.

The pulleys that directly affect belt adjustment and noise are the tensioner and idler pulleys. A worn tensioner will cause the belt to slip and reduce accessory efficiency. For example, alternator charging output may be reduced which may wear the battery down. Your vehicle may not start and the CHECK ENGINE light may illuminate. Slippage will also wear the belt and cause a squealing noise, as well as generate heat that will reduce the life of accessory pulley bearings. Many tensioners also include a dampening mechanism to control vibration. A worn damper will allow belt slap, which can also cause pulley bearings to fail.

Pulley misalignment can cause belt chirp. Worn tensioner and idler pulleys can cause misalignment, which can also create excessive heat that wears the belt and the pulley bearings. Spraying water on the rib side of a serpentine belt can help determine whether a noise is a chirp or squeal. If the noise temporarily subsides, it’s a chirp caused by misalignment. If it gets louder, it’s a squeal caused by reduced belt tension. But you won’t have to make such distinctions if you replace the automatic tensioner and idler pulley(s) along with the serpentine belt - our accessory drive belt kits provide everything needed.

During deceleration, the spinning alternator creates drag, creating strain on the serpentine belt and tensioner. Many manufacturers use alternator decoupler pulleys, which allow the alternator to freewheel during deceleration, eliminating strain and increasing belt and tensioner lifespan. There are One-Way Clutch (OWC) and Overrunning Alternator Decoupler (OAD) pulleys. Both function similarly, but the OAD also contains a mechanism to reduce vibration. Many OE dealers do not service these pulleys separately from the alternator, but we have them, along with the installation tools, so you can save money.

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    This article will guide you through a generic tune up on most any car or light duty gasoline-powered vehicle built within the last 20 years or so. We will presume that you are tuning up your engine because it has reached the mileage or time point to do so, and that you are NOT performing a tune up to cure an engine performance defect. We make this distinction because not all running/performance issues will be solved via a simple tune up.
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    Internal combustion engines are extremely complex and feature a wide array of components that rotate, move up and down, pump, seal, or remain stationary. When repairing or rebuilding your engine, you will come across many different terms when referencing repair manuals and ordering parts. We know it can be confusing, especially when the repair is complex. Even if you are paying a professional to do the work, it’s good to be conversant with the topic. In order to help you understand the terminology of engine components, we’ve created the following glossary, listed in alphabetical order.

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Engine Pulleys, Harmonic Balancers Reviews

Average rating:  5  4.8 - 12 reviews
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Easy to install, very good quality, would definitely recommend purchasing from here.
TPosted by Tristan (Williston, ND) /
2009 Mitsubishi Lancer
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