Buy Buick Lucerne Accessory Drive Belt Tensioner Assemblys

The accessory drive belt tensioner assembly-also called a serpentine belt tensioner, drive-belt pulley tensioner, or simply belt tightener-keeps the single "snake-like" belt on your Buick Lucerne tight so it can spin the alternator, power-steering pump, water pump, A/C compressor, and more. The Lucerne was built from 2006-2011 with 3.8 L, 3.9 L, and 4.6 L engines, each using a spring-loaded automatic tensioner to hold the poly-V belt at the right pressure. A healthy tensioner stops squeal, prevents stalling accessories, and helps the belt last longer. (Wikipedia, Wikipedia)

A tensioner is a small arm and pulley that rides on the back of the serpentine belt. Inside the arm is either a coil spring or a tiny hydraulic damper that keeps constant pressure on the belt as it stretches and shrinks with engine speed and heat. If this "belt pressor" lets go, the belt slips and every accessory can quit. (Industrias Dolz)

All Buick Lucerne sedans-model-years 2006, 2007, 2008, 2009, 2010, and 2011-use a main accessory belt tensioner.

• 3.8 L Series III V6 (2006-2008)
• 3.9 L "High-Value" V6 (2009-2011)
• 4.6 L Northstar V8 (2006-2011)

The 4.6 L also carries a tiny secondary tensioner for its water-pump "stretch" belt. (Wikipedia, Cadillac Forums)

The belt leaves the crank pulley, winds around up to seven other pulleys in a "serpentine" path, and finally meets the tensioner pulley. When the spring inside the tensioner arm moves, it takes up slack so the grooved belt can grip each pulley without slipping. That constant load also damps vibration, protecting bearings. (Wikipedia, Industrias Dolz)

• Squeal or Chirp at Start-up - A loose belt slips and squeals; chirping often means pulley mis-alignment. (YouTube, GMB North America, Inc.)
• Belt Flap or Bounce - You may see the tensioner arm shaking. (YouTube)
• Dim Lights or Weak Steering - Loss of alternator or power-steering speed tells you the belt is not tight. (YourMechanic)
• Frayed or Glazed Belt - Uneven wear on the belt ribs hints at a worn bearing inside the tensioner. (GMB North America, Inc.)

Over time the spring inside the arm sags, bearings dry out, or road grit gets past the seal. Oil and coolant leaks soften the rubber belt, letting it slip and over-heat the pulley. Mis-aligned accessory brackets can also push the pulley off-center, creating that tell-tale chirp. (, Industrias Dolz)

1. Look & Listen - With the engine running, watch the pulley; it should spin smoothly without shaking.
2. 90-Degree Twist Test - On the longest belt span, you should be able to twist only halfway (about a quarter-turn). Any more may mean low tension. (Bob Is The Oil Guy)
3. Check the Arm Travel - Shut the engine off, place a 3⁄8-inch or 1⁄2-inch drive ratchet in the square hole, and sweep the arm through its full range. It should move smoothly and snap back. (Cadillac Forums)
4. Spin the Pulley by Hand - Feel for grit or roughness; any grinding sound calls for replacement. (YouTube)

1. Follow the belt-routing sticker under the hood or the diagram in the owner's manual. (ManualsLib)
2. Insert a ratchet into the tensioner hub and rotate to relieve tension.
3. Slip the old serpentine belt off and unbolt the tensioner (usually one central bolt).
4. Install the new tensioner; torque to spec (see next section).
5. Route the new belt and slowly release the tensioner. Check alignment on every pulley.

Tip: On the Northstar V8, you'll also replace the short water-pump belt and its tiny tensioner on the back of the engine. (Cadillac Forums)

← scroll table horizontally →

Always tighten the center bolt only; the pulley bolt is pre-set. (torkspec.com, gmforum.com)

Inspect the belt system at every oil change. Most drive belts last 60,000 miles, but the tensioner may survive 90,000 miles or more-unless noise appears first. Replace the belt and tensioner together to save labor and avoid repeat squeals. (YourMechanic)

• Work on a cool engine to avoid burns.
• Keep fingers and tools clear of the belt path when cranking the engine.
• Wear eye protection; the spring-loaded arm can snap back quickly.

• Buick Lucerne model overview - engine list & specs. (Wikipedia)
• How a serpentine belt works - belt basics. (Wikipedia)
• Detailed tensioner function guide - mechanical vs hydraulic designs. (Industrias Dolz)
• GM 3800 torque chart - 37 ft-lb spec. (torkspec.com)
• Service-life article - average mileage and warning signs. (YourMechanic)
• Squeak troubleshooting steps - diagnosing chirps vs squeals. (GMB North America, Inc.)
• Forum walk-through for Northstar belt swap. (Cadillac Forums)
• Rule-of-thumb tension check. (Bob Is The Oil Guy)