2018 International LT — Serpentine Belt Routing & Length

Quick answer

• Belt length: Varies by engine and accessory package on the 2018 International LT (A26 vs. Cummins X15, alternator output, with/without dedicated AC). Expect a single 10‑rib Micro‑V belt; length commonly falls in the ~100–112 inch range. Always confirm by VIN (for A26) or Cummins ESN (for X15) before ordering.
• Rib count: Typically 10‑rib for both A26 and X15 applications.
• OEM belt part number: Varies by engine/build. Confirm with your International dealer (VIN) for A26, or Cummins distributor (ESN) for X15.
• Aftermarket cross‑refs:
  • Gates FleetRunner K10‑series (length matched to your build; e.g., K10xxxxHD)
  • Dayco Gold Label HD (10‑rib Micro‑V matched to length)
  • Continental/ContiTech 10PK‑series (length matched to build)
• Automatic tensioner PN: Varies by engine and bracket set (common suppliers: Litens, Gates DriveAlign, Dayco). Verify by VIN/ESN.
• Idler pulley PN: Varies by engine/accessory layout. Verify by VIN/ESN.

Note: The 2018 LT commonly shipped with either the International A26 12.4L or the Cummins X15. Front accessory drive layouts and lengths differ; use the truck’s VIN (A26) or the Cummins Engine Serial Number (X15) to get exact part numbers.

Belt routing

Because we can’t show an image here, use this text path and take a clear photo of your existing belt before removal.

Starting at the crankshaft pulley (harmonic balancer):

1. From the crank pulley, route the grooved side of the belt down and around the A/C compressor pulley.
2. From the A/C compressor, go up and over a smooth idler pulley (back side of the belt on the smooth idler).
3. From that idler, continue to the alternator pulley (grooved side on the alternator).
4. From the alternator, route down to the power steering pump pulley (grooved side).
5. From the power steering pump, wrap around the water pump pulley. Many HD water pumps are smooth; if yours is smooth, the back side of the belt rides here. If it’s grooved, use the ribbed side. Match ribs to grooves and back side to smooth every time.
6. From the water pump, finish the loop over the automatic tensioner pulley (usually smooth—back side of the belt) and back to the crank pulley.

Keep the ribs aligned in every grooved pulley and the belt’s back side on smooth idlers/tensioner. If your engine has an extra decoupler or an additional idler, follow the same groove/back‑side rule to maintain the proper S‑path.

How to replace the serpentine belt

Tools: serpentine belt tool or a long 1/2‑inch (some are 3/8‑inch) breaker bar to unload the tensioner; basic hand tools; a mirror/flashlight.

1. Document the routing. Photograph the belt and sketch the path. Confirm which pulleys are smooth versus grooved.
2. Unload the tensioner. Insert the square drive of your tool into the tensioner and rotate it in the direction that loosens the belt. Slide the belt off the easiest accessible smooth idler first.
3. Remove the belt. Feed it out of the accessory stack, noting any tight clearances.
4. Inspect components. Spin the idler(s) and tensioner pulley; they should be smooth and quiet with no wobble. Check the tensioner arm for smooth travel and proper return. Inspect all pulleys for alignment and damage.
5. Install the new belt. Route it according to your photo and the text path above, leaving the easiest smooth pulley for last. Ensure the ribs are fully seated in every grooved pulley.
6. Re‑tension. Rotate the tensioner again and slip the belt over the final pulley. Slowly release the tensioner. Double‑check that the belt is centered on every pulley.
7. Start and verify. Start the engine and observe for 30–60 seconds. The belt should track true with no chirp, squeal, or flutter. Recheck after a short road test.

Tip: If the belt sits one rib over on any pulley, shut down and correct it immediately. Mis‑seating will shred the belt quickly.

Replacement interval

• Inspect at every PM service. On highway tractors, a quality HD belt may last 100k–150k miles, but contamination, heat, and pulley wear can shorten that.
• Replace at the first signs of glazing, cracking, chunking, or if the tensioner shows loss of travel or bounce. As a preventive rule of thumb, many fleets replace the belt and tensioner/idlers together around 100k–150k miles or 2–3 years, depending on duty cycle.

Signs of a failing belt or tensioner

• Chirping or squealing at start‑up or when turning the wheel (load change)
• Glazed, shiny ribs; rubber dust around the front cover
• Cracks, missing chunks, frayed belt edges, or rib separation
• Belt flutter at idle; tensioner arm bouncing or not returning smoothly
• Accessory underperformance (low alternator output, heavy steering, intermittent A/C) especially under load
• Coolant or oil contamination on the belt (replace the belt and fix the leak)

Engine‑option variation

• International A26: Typically a single 10‑rib belt with an automatic tensioner and one or more smooth idlers. Length and bracketry vary by alternator amperage and A/C configuration. Use VIN to source exact OEM PN and length.
• Cummins X15: Also typically a single 10‑rib belt. Length and tensioner/idler specifics vary by accessory drive and alternator options. Use the Cummins ESN to retrieve the exact belt, tensioner, and idler part numbers.

When in doubt, measure the old belt (if intact), count ribs (10 for most), and confirm with VIN/ESN. Matching by length, rib count, and engine family will get you the correct Gates/Dayco/Continental cross‑reference.

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