Engine Pulleys

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. You can 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. If you want to reduce your accessories’ power consumption without negatively affecting function, you can reduce the weight of your pulleys and by changing their diameter. We offer aluminum pulleys that are much lighter than the original equipment pulleys, without any reduction in strength. Their light weight not only results in a horsepower increase, but the reduced rotational mass also improves throttle response.

The accessories on modern vehicles are generally driven by a single serpentine belt, but older performance vehicles used multiple V-belts, and even if tensioned properly, centrifugal force would often cause these belts to jump during high RPM shifts. Then as now, the answer to this problem is a deep groove pulley, but you don’t have to spend a lot of time and money searching for an original part that may have been discontinued long ago. We can supply you with pulleys that feature deep, precision machined grooves for secure belt retention even at extreme RPM changes, and some are underdriven so you gain horsepower as well.