2021 GMC Sierra 1500: Serpentine Belt Replacement Guide

Quick Answer: 2021 GMC Sierra 1500 Serpentine Belt Parts

Note on Engine Variations: The 2021 GMC Sierra 1500 was available with several engine options (2.7L I4, 4.3L V6, 5.3L V8, 6.2L V8, and 3.0L I6 Diesel). Part numbers can vary between these engines. Always verify your truck's specific engine before purchasing parts. The following numbers are for the common 5.3L and 6.2L V8 engines unless specified otherwise.

• Serpentine Belt Length & Rib Count: 6-rib design. Length can vary, so matching to your specific engine and accessory configuration is critical.
• OEM Serpentine Belt Part Number: GM 12657482
• Aftermarket Belt Cross-References:
  • Gates K060923
  • Dayco 5060923
  • Continental 4060923
• OEM Automatic Belt Tensioner Part Number: GM 12670923
• OEM Idler Pulley Part Number: GM 12626039

Belt Routing for 2021 GMC Sierra 1500

Properly routing the serpentine belt is critical for the function of your engine's accessories. An incorrectly routed belt can cause damage to the belt and pulleys. Before you remove the old belt, we strongly recommend taking a clear photograph of the routing path from a couple of different angles.

For the V8 engines, the belt path is as follows:

1. Starts at the main crankshaft pulley at the bottom of the engine.
2. Wraps around the A/C compressor pulley.
3. Goes up and around the smooth idler pulley.
4. Travels over the top of the alternator pulley.
5. Comes down to the grooved power steering pump pulley.
6. Goes around the smooth water pump pulley.
7. Finally, loops under the spring-loaded automatic tensioner before returning to the crank pulley.

How to Replace the Serpentine Belt

Replacing the serpentine belt on a 2021 Sierra is a manageable task for a DIYer with the right tool. The key is releasing the tension from the automatic belt tensioner.

You will need a serpentine belt tool, which is a long, thin ratchet with various socket and crowfoot attachments. In many cases, a standard 3/8" drive breaker bar can also fit into the square opening on the face of the tensioner.

1. Safety First: Ensure the engine is cool. Disconnect the negative battery terminal.
2. Locate the Tensioner: The tensioner is a spring-loaded pulley designed to keep the belt tight. On the V8 engines, it is typically located on the driver's side of the engine.
3. Release Tension: Fit your serpentine belt tool or breaker bar into the square hole on the tensioner body. Rotate the tool clockwise to swing the tensioner pulley away from the belt, releasing the tension.
4. Remove Old Belt: While holding the tensioner, carefully slip the old belt off one of the pulleys (the alternator or water pump is usually easiest).
5. Install New Belt: Following your photo and the routing diagram above, carefully thread the new belt around the pulleys, saving the final pulley (a smooth one like the water pump) for last.
6. Apply Tension: Double-check that the belt is correctly seated in all the ribbed pulley grooves. Slowly release the tensioner to apply pressure to the new belt.
7. Final Check: Inspect the belt path one last time. Reconnect the battery, start the engine, and let it run for a minute to ensure everything is operating smoothly.

Replacement Interval

Modern serpentine belts are durable. There is no universally mandated replacement interval from GM. A good rule of thumb is to have the belt inspected during every oil change and plan for replacement between 60,000 and 100,000 miles. However, this can be affected by operating conditions. Trucks in harsh, dusty, or extremely hot climates may require more frequent replacement.

Signs of a Failing Belt or Tensioner

Listen and look for these common warning signs:

• Squealing or Chirping Noises: This is the most common symptom, often worse on cold starts or during sharp turns.
• Visible Wear: Check the belt for cracks, fraying, glazing (shiny spots), or missing ribs.
• Accessory Malfunction: A slipping belt can cause issues like a flickering battery light (alternator not spinning correctly), stiff steering (power steering pump issue), or engine overheating (water pump not turning).
• Tensioner Noise: A grinding or rattling noise from the tensioner pulley indicates a failing bearing.
• "Bouncing" Tensioner: If you see the tensioner arm vibrating or bouncing erratically while the engine is running, the internal spring is weak and it should be replaced.

If you're not comfortable performing this service yourself, Repairius can help.

Find a trusted shop on Repairius.