2021 Nissan Altima Serpentine Belt - Routing, Diagram, and Replacement

Quick Answer: 2021 Altima Serpentine Belt Specifications

This guide covers the two engine options for the 2021 Nissan Altima: the common 2.5L 4-cylinder (PR25DD) and the 2.0L VC-Turbo (KR20DDET). Part numbers are different between these engines.

For the 2.5L 4-Cylinder Engine (PR25DD):

• Belt Length: ~1226mm (48.25 inches)
• Rib Count: 6-rib
• OEM Belt Part Number: Nissan 11720-6CA0A
• Aftermarket Belt Cross-References: Gates K060475, Dayco 5060475, Continental 4060475
• Auto-Tensioner Assembly Part Number: Nissan 11955-6CA0B (Aftermarket e.g., Gates 39423)
• Idler Pulley: The 2.5L engine's main drive does not use a separate idler pulley. The pulley is integrated into the tensioner assembly.

For the 2.0L VC-Turbo Engine (KR20DDET):

• OEM Belt Part Number: Nissan 11720-5NA0A
• Aftermarket Belt Cross-References: Gates K060482, Dayco 5060482
• Auto-Tensioner Assembly Part Number: Nissan 11955-5NA0A

Belt Routing

Properly routing the serpentine belt is critical for the function of your engine's accessories. A misrouted belt can cause damage or slip off the pulleys. Because it can be difficult to remember the correct path, we strongly recommend taking a clear photograph of the belt's routing before you begin removal.

Unlike older vehicles, the 2021 Altima uses an electric power steering system, so there is no hydraulic power steering pump pulley in the serpentine belt path.

The belt routing for the 2021 Nissan Altima with the 2.5L engine is as follows:

1. The belt wraps around the main crankshaft pulley at the bottom of the engine.
2. From the crankshaft, the belt travels up to the A/C compressor pulley.
3. From the A/C compressor, it moves across to the alternator pulley.
4. From the alternator, it goes down to the water pump pulley.
5. Finally, it routes around the tensioner pulley, which maintains the correct belt tension.

How to Replace the Serpentine Belt

Replacing the serpentine belt is a manageable task for many DIYers. The key is having the right tool to release the belt tension.

Tool Required: A serpentine belt tool kit or a long-handled 3/8-inch breaker bar.

The automatic belt tensioner has a 3/8" square hole designed to accept a breaker bar or the corresponding adapter from a belt tool kit. To release the tension, you will fit the tool into this square hole and rotate the tensioner arm away from the belt. This will create enough slack to slip the old belt off the pulleys.

Once the old belt is removed, carefully thread the new belt onto the pulleys following the routing diagram you photographed earlier. It's often easiest to leave a smooth pulley, like the water pump, for last. Once the belt is routed correctly on all the ribbed pulleys, slip it over the final smooth pulley while holding the tensioner in the released position. Double-check that the belt is centered on all pulleys before slowly releasing the tensioner and removing your tool.

Replacement Interval

Nissan's official maintenance schedule for the 2021 Altima specifies inspecting the drive belt periodically (typically during routine oil change services) for signs of wear. There is no mandated replacement time or mileage.

However, as a matter of preventative maintenance, most ASE-certified technicians recommend replacing the serpentine belt every 60,000 to 90,000 miles. Belts are made of durable EPDM rubber, but they still degrade over time from heat, friction, and environmental factors. Replacing it proactively can prevent a sudden failure that leaves you stranded.

Signs of a Failing Belt or Tensioner

A failing belt or tensioner will almost always provide audible or visible clues before it fails completely.

Signs of a Bad Serpentine Belt:

• Squealing Noises: A high-pitched squeal, especially when starting the engine, turning on the A/C, or during cold, damp weather.
• Visible Wear: Look for cracks, glazing (a shiny, smooth appearance on the ribbed side), fraying edges, or any chunks of rubber missing from the ribs.

Signs of a Bad Belt Tensioner:

• Rattling or Grinding: A chattering, rattling, or grinding sound coming from the tensioner pulley indicates a worn-out bearing.
• Excessive Movement: While the engine is idling, watch the tensioner arm. Some movement is normal, but if it is jumping or vibrating erratically, the internal damping mechanism is likely worn out.
• Belt Tracking Issues: If the belt consistently walks off the edge of the tensioner pulley, the tensioner assembly may be misaligned or failing.

A bad tensioner can fail to keep proper tension on the belt, causing slippage, or its pulley bearing can seize, which will shred the belt and may leave you stranded. If you are replacing a high-mileage belt, it is wise to consider replacing the tensioner at the same time.

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