2017 Kenworth T680 Serpentine Belt Routing & Length

Quick Answer: 2017 Kenworth T680 Serpentine Belt

Identifying the correct serpentine belt and associated components for your 2017 Kenworth T680 is crucial for optimal engine performance and avoiding breakdowns. The T680 comes with various engine options, including the PACCAR MX-13 and Cummins ISX15. The information below focuses on the most common configurations, but always verify part numbers with your specific engine serial number.

• Belt Length: Varies by engine. For PACCAR MX-13, typically around 125.5 inches (3188 mm). For Cummins ISX15, typically around 120.0 inches (3048 mm).
• Rib Count: 8-rib (common for heavy-duty applications)
• OEM Belt P/N (PACCAR MX-13): 1938096PE (Verify with VIN)
• Aftermarket Cross-references (PACCAR MX-13, example length):
  • Gates K081255 (Example, always confirm exact length)
  • Dayco 5081255 (Example, always confirm exact length)
  • Continental Elite 4081255 (Example, always confirm exact length)
• OEM Belt P/N (Cummins ISX15): 3698774 (Verify with VIN)
• Aftermarket Cross-references (Cummins ISX15, example length):
  • Gates K081200 (Example, always confirm exact length)
  • Dayco 5081200 (Example, always confirm exact length)
  • Continental Elite 4081200 (Example, always confirm exact length)
• Auto-Tensioner P/N (PACCAR MX-13): 1944686PE (Verify with VIN)
• Idler Pulley P/N (PACCAR MX-13): 1938507PE (Verify with VIN)
• Auto-Tensioner P/N (Cummins ISX15): 3692485 (Verify with VIN)
• Idler Pulley P/N (Cummins ISX15): 3698822 (Verify with VIN)

Always verify part numbers against your specific engine VIN or serial number to ensure correct fitment.

Belt Routing: 2017 Kenworth T680 PACCAR MX-13 Engine

Given the complexity of heavy-duty engine layouts, it is imperative to photograph your existing belt routing before removal. While exact routing can vary slightly based on accessories, a common path for the PACCAR MX-13 engine is as follows:

1. Crankshaft Pulley: The largest pulley at the bottom, which drives all other accessories. The belt will likely begin by wrapping around this pulley.
2. A/C Compressor: From the crankshaft, the belt often routes to the air conditioning compressor pulley.
3. Idler Pulley (lower): After the A/C compressor, the belt may pass over or under an idler pulley, which helps maintain tension and guide the belt.
4. Alternator: The belt then typically wraps around the alternator pulley, powering the vehicle's electrical system and charging the battery.
5. Power Steering Pump: Next in the path is often the power steering pump pulley.
6. Water Pump: The belt will then route to the water pump, which circulates coolant through the engine.
7. Idler Pulley (upper): Depending on the configuration, there might be another idler pulley before the tensioner.
8. Automatic Tensioner: Finally, the belt will wrap around the automatic tensioner pulley. This spring-loaded pulley applies constant tension to the belt, preventing slippage.

Remember, this is a generalized description. Take multiple clear photos from different angles before you begin any work.

How to Replace the Serpentine Belt

Replacing the serpentine belt on a 2017 Kenworth T680 requires some mechanical aptitude and the right tools. Ensure the engine is cool before starting.

1. Safety First: Disconnect the battery's negative terminal to prevent accidental starting or electrical shorts.
2. Observe and Photograph: As mentioned, take clear photos of the existing belt's routing to ensure correct reinstallation.
3. Locate the Tensioner: Identify the automatic belt tensioner. It will have a square drive hole (typically 1/2-inch or 3/8-inch, check your specific tensioner) or a hexagonal bolt head.
4. Relieve Tension: Using a serpentine belt tool or a long breaker bar/ratchet with the appropriate socket, insert it into the tensioner's square drive or onto the hex bolt. Rotate the tensioner to relieve tension on the belt. This will allow you to slip the old belt off the pulleys.
5. Remove Old Belt: Carefully remove the old belt from all pulleys.
6. Inspect Pulleys: While the belt is off, inspect all pulleys (alternator, A/C, power steering, idlers, water pump) for any signs of wear, wobbling, or excessive noise when spun by hand. Check for bearing play.
7. Install New Belt: Route the new belt according to your photographs or the routing diagram (if available). Start by placing the belt around all stationary pulleys except the tensioner or an easily accessible idler.
8. Tension the Belt: Once mostly routed, again apply pressure to the tensioner with your tool, and slip the belt over the final pulley.
9. Verify Routing: Double-check that the belt is correctly seated in all pulley grooves and that the routing matches your photographs.
10. Reconnect Battery: Reconnect the battery's negative terminal.
11. Test Run: Start the engine and let it run for a few minutes. Listen for any squealing or unusual noises. Turn off the engine and re-inspect the belt for proper alignment.

Replacement Interval

For heavy-duty trucks like the Kenworth T680, serpentine belt replacement intervals can vary significantly based on operating conditions, engine hours, and manufacturer recommendations. Generally, a good preventive maintenance schedule suggests inspection every 50,000 miles or annually, and replacement every 150,000 to 200,000 miles, or every 3 to 4 years, whichever comes first. However, always refer to your Kenworth T680 owner's manual or maintenance guide for specific recommendations for your engine. Frequent inspections are key given the critical role of these belts in a commercial vehicle.

Signs of a Failing Belt or Tensioner

Ignoring a failing serpentine belt or tensioner can lead to significant issues, including loss of power steering, A/C, charging, and even engine overheating.

Signs of a Failing Belt:

• Squealing or Chirping Noises: Especially on startup, during turns (power steering), or when the A/C is engaged. This indicates slippage.
• Cracks or Fraying: Visible cracks on the ribbed side of the belt, missing chunks of ribs, or fraying along the edges.
• Glazing: A shiny, hardened appearance on the belt's surface, indicating wear and reduced grip.
• Power Steering Loss: If the belt driving the power steering pump fails, steering will become very difficult.
• Overheating: A failed belt driving the water pump will lead to engine overheating.
• Battery Not Charging: If the belt driving the alternator fails, your battery will not charge.

Signs of a Failing Tensioner:

• Excessive Belt Vibration/Flapping: The belt appears to be vibrating excessively or flapping, especially at idle, indicating the tensioner isn't maintaining proper tension.
• Grinding or Squealing from Tensioner: Noises directly from the tensioner pulley itself often indicate a failing bearing within the pulley.
• Tensioner Misalignment: The tensioner pulley appears to be tilted or misaligned, which can cause premature belt wear.
• Belt Slippage: Even with a good belt, a weak tensioner won't apply enough force, leading to squealing and slippage.
• Play in Tensioner Arm: With the engine off, try to move the tensioner arm by hand. Excessive play or looseness is a sign of a worn tensioner.

Addressing these issues promptly will prevent more costly repairs and ensure the reliability of your Kenworth T680.

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