engine
Serpentine Belt Tensioner
for 2007 Ram 3500 5.9L I6 Cummins · 4WD
Difficulty
Easy
Time
1.2 h
Tools
6
Steps
10
✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.
This procedure covers the removal and replacement of the serpentine belt tensioner on the 5.9L Cummins diesel engine, including belt removal and reinstallation.
Warnings
⚠Allow engine to cool completely before starting work to avoid burns from hot components
⚠The belt tensioner is spring-loaded and will apply significant force when released
ℹ️Inspect the serpentine belt for cracks, glazing, or fraying while performing this service
Tools required
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.
Parts
- Serpentine belt tensioner assembly × 1 — Use OEM specification
- Serpentine belt (if worn or damaged) × 1 — Use OEM specification
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.
Preparation
- Ensure engine is cool to the touch
- Disconnect negative battery cable to prevent accidental starter engagement
- Take a photo or draw a diagram of the belt routing path for reference during reinstallation
- Verify replacement tensioner matches the original in design and mounting configuration
Procedure
- 1Access the serpentine belt areaOpen the hood and secure it in the upright position. Locate the serpentine belt routing diagram on the fan shroud or radiator support. If the diagram is missing or unclear, take a detailed photo of the belt routing before removal.
- 2Release belt tensionLocate the belt tensioner pulley on the passenger side of the engine. Insert a 3/8" drive ratchet or breaker bar into the square hole on the tensioner arm. Rotate the tensioner in the direction that swings the pulley away from the belt (typically clockwise on the 5.9L Cummins) to release tension. Verify the correct direction by observing which way the arm moves off the belt before applying full force. The tensioner arm will swing through a limited arc; move it only as far as needed to relieve belt tension.
- 3Remove serpentine beltWhile maintaining pressure on the tensioner with the ratchet, slip the belt off the alternator pulley or the easiest accessible pulley. Slowly release tension on the tensioner arm. Remove the belt from all remaining pulleys and withdraw it from the engine compartment. Inspect the belt for wear, cracks, or damage.
- 4Remove tensioner mounting boltLocate the tensioner mounting bolt at the center of the tensioner assembly. Use the correct size socket (commonly 13mm or 15mm on the 5.9L Cummins — verify on your vehicle) to remove the tensioner mounting bolt. The bolt threads into the engine block. Keep this bolt as it may be reused with the new tensioner depending on the replacement part supplied.
- 5Remove tensioner assemblyPull the tensioner assembly straight out from the engine block mounting point. The tensioner may have a locating pin or alignment feature that fits into the block. Inspect the mounting surface on the engine block for damage or debris and clean if necessary.
- 6Compare old and new tensionersPlace the old tensioner next to the new tensioner and verify that the pulley design, mounting hole location, and overall dimensions match. Check that the spring tension arm operates smoothly on the new tensioner and returns to the rest position properly.
- 7Install new tensionerAlign the new tensioner with the mounting hole on the engine block, ensuring any locating pins or alignment features are properly seated. Insert the mounting bolt and thread it by hand to avoid cross-threading. Tighten the tensioner mounting bolt to the manufacturer-specified torque (typically around 35 ft-lbs for an M10 bolt on this engine — verify against OEM documentation) using a torque wrench.
- 8Route new or existing beltBeginning at the crankshaft pulley, route the serpentine belt around all pulleys according to the routing diagram or reference photo. Leave the alternator or easiest accessible pulley for last. Ensure the belt is properly seated in all pulley grooves and not riding on pulley edges.
- 9Install belt onto final pulleyUsing a 3/8" drive ratchet in the tensioner square hole, rotate the tensioner in the release direction (typically clockwise on the 5.9L Cummins — verify) to create slack. Slip the belt over the final pulley while maintaining tension on the tensioner. Slowly release the tensioner to apply proper tension to the belt.
- 10Verify belt installationVisually inspect all pulleys to confirm the belt is centered in each groove and not twisted. Manually rotate the crankshaft one full revolution by turning the crankshaft pulley bolt clockwise using a socket. Observe the belt movement to ensure it tracks properly on all pulleys without slipping or misalignment.
Reassembly
- Reconnect the negative battery cable
- Double-check that all tools have been removed from the engine compartment
- Ensure no loose bolts or hardware remain near the belt path
Verification
- Start the engine and allow it to idle while observing the serpentine belt operation
- Listen for any squealing, chirping, or abnormal noises from the belt area
- Verify the belt tracks properly on all pulleys without slipping or walking off the edges
- Check that all accessories (alternator, air conditioning compressor, power steering pump) are operating normally
- After a short test drive, recheck belt tension and alignment while the engine is off and cool