2021 Ford F-350 Super Duty Serpentine Belt Routing & Replacement Guide

Quick Answer

For most 2021 Ford F-350 Super Duty models with the 6.7L Power Stroke diesel engine, the serpentine belt specifications are:

• Belt Length: Approximately 106.5 inches
• Rib Count: 6-rib
• OEM Belt PN: Ford HC3Z-8620-A
• Gates Aftermarket Cross-reference: K061065
• Dayco Aftermarket Cross-reference: 5061065
• Continental Elite Aftermarket Cross-reference: 4061065
• Auto-Tensioner PN: Ford HC3Z-6B209-A (Gates 38407, Dayco 89407)
• Idler Pulley PN: Ford HC3Z-8678-A (Gates 36173, Dayco 89201)

Note: These part numbers are for the 6.7L Power Stroke diesel engine. The 7.3L Godzilla and 6.2L gasoline engines will have different part numbers and routing. Always verify part numbers with your VIN for exact fitment.

Belt Routing

Before you begin any work, it's highly recommended to take a clear photograph of the current belt routing. This will serve as an invaluable reference during reinstallation.

The serpentine belt on your 2021 F-350 Super Duty (6.7L Power Stroke) typically follows this path:

1. Starting from the crankshaft pulley (the largest pulley at the bottom, directly connected to the engine).
2. The belt will then go up and over the A/C compressor pulley.
3. From the A/C compressor, it will route to an idler pulley (a smooth pulley that guides the belt).
4. Next, it will wrap around the alternator pulley.
5. From the alternator, the belt generally moves down to the power steering pump pulley.
6. Then, it will route to the water pump pulley.
7. Finally, it will pass around the automatic tensioner pulley, which maintains proper belt tension.

How to Replace the Serpentine Belt

Replacing the serpentine belt on your F-350 requires a few basic tools and a bit of patience. Always ensure the engine is off and cool before starting.

1. Locate the Automatic Belt Tensioner: This is the pulley with an arm that provides tension to the belt. It usually has a square hole for a serpentine belt tool or a 3/8-inch drive breaker bar.
2. Relieve Tension: Insert a serpentine belt tool or a 3/8-inch breaker bar into the square opening on the tensioner. Rotate the tensioner arm to release the tension on the belt. This will allow you to slip the belt off the pulleys.
3. Remove the Old Belt: Once the tension is relieved, carefully remove the belt from all the pulleys, starting with an easy-to-reach pulley like the idler or alternator.
4. Inspect Pulleys: While the belt is off, inspect all pulleys for any signs of wear, wobbling, or excessive play. Also, check for any oil or fluid leaks that might have contaminated the old belt.
5. Route the New Belt: Following the photograph you took earlier and the routing description above, carefully route the new serpentine belt around all the pulleys, leaving the tensioner pulley for last or a similar easy-to-access pulley.
6. Apply Tension: Once the belt is correctly routed on all other pulleys, use your serpentine belt tool or breaker bar to release the tensioner, allowing it to apply tension to the new belt. Double-check that the belt is seated properly in all the pulley grooves.
7. Start the Engine: Briefly start the engine to ensure the belt is tracking correctly and there are no abnormal noises. Turn the engine off and re-check the belt for proper alignment.

Replacement Interval

Ford generally recommends inspecting the serpentine belt at every oil change or major service interval (typically every 10,000 to 15,000 miles or 12 months, whichever comes first). However, the replacement interval can vary based on driving conditions and engine type.

For most F-350 Super Duty trucks with the 6.7L Power Stroke engine, a replacement every 60,000 to 100,000 miles is a good general guideline, or sooner if signs of wear are observed. It's always best to consult your owner's manual for the manufacturer's specific recommendations for your exact model and engine.

Signs of a Failing Belt or Tensioner

Ignoring a failing serpentine belt or tensioner can lead to a breakdown, as many critical engine components rely on this belt for power. Here are some signs to watch for:

• Squealing or Chirping Noises: This is one of the most common signs. It can indicate a worn-out belt, a misaligned pulley, or a failing tensioner that isn't maintaining proper tension.
• Cracked or Frayed Belt: Visually inspect the belt for cracks, fraying, missing ribs, glazing (a shiny, hardened appearance), or chunks missing from the ribs.
• Loss of Power Steering, A/C, or Charging: If the serpentine belt breaks, you will immediately lose power to all accessories it drives, including the power steering, air conditioning, and the alternator (leading to a dead battery).
• Wobbling or Excessive Play in Pulleys: A failing tensioner can cause the belt to be loose, leading to a wobbling idler or tensioner pulley. You might also notice excessive play when trying to move the tensioner or idler pulleys by hand.
• Grinding Noises from Pulleys: This can indicate a failing bearing within an idler pulley, the tensioner, or one of the driven components.
• Overheating: While less common for belt issues directly, if the water pump is driven by this belt and the belt slips significantly or breaks, the engine can overheat.

Timely inspection and replacement of these components are crucial for the reliable operation of your F-350 Super Duty.

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