Replace the timing chain tensioner on the 6.7L Cummins diesel engine, requiring removal of front accessories, timing cover, and careful alignment of timing marks.

Warnings

Tools required

Parts

• Timing chain tensioner × 1 — Use OEM Cummins specification
• Timing cover gasket × 1 — Use OEM specification
• Valve cover gasket × 1 — Use OEM specification
• Crankshaft front seal × 1 — Use OEM specification
• Tensioner mounting bolt × 1 — Use OEM specification
• Camshaft seal × 1 — Use OEM specification

Fluids

• Mopar OAT Coolant (Purple) — 18 qt
• Mopar 5W-20 Synthetic Blend — 13 qt

Preparation

1. Ensure engine is completely cool before starting work
2. Disconnect both battery terminals, negative first
3. Raise and safely support vehicle on jack stands
4. Remove engine cover and beauty covers
5. Install engine support fixture to support engine weight
6. Drain engine coolant into appropriate container
7. Drain engine oil into appropriate container
8. Remove radiator upper and lower hoses
9. Remove fan shroud and cooling fan assembly
10. Take photos of belt routing for reference

Procedure

1. 1

   Remove serpentine belt and accessories
   Remove the serpentine belt by releasing the tensioner. Remove the power steering pump and bracket (leave hoses connected and secure aside). Remove the A/C compressor mounting bolts and secure the compressor aside without disconnecting refrigerant lines. Remove alternator and mounting bracket.
2. 2

   Remove crankshaft pulley
   Use a breaker bar on the crankshaft pulley bolt to loosen (counterclockwise). You may need to lock the flywheel from underneath the vehicle. Once loose, remove the bolt completely. Use a harmonic balancer puller to remove the crankshaft pulley from the crankshaft snout. Do not use impact tools or pry against the pulley.
3. 3

   Remove valve cover
   Disconnect injector electrical connectors and any breather hoses connected to the valve cover. Remove valve cover bolts in reverse of tightening sequence. Carefully lift valve cover off and inspect gasket sealing surfaces. Clean any residual gasket material from both cover and head surfaces.
   Torque spec

   Valve Cover Bolts10 Nm (7 lb-ft)
4. 4

   Remove timing cover
   Remove all timing cover bolts, noting the locations of different length bolts (8mm and standard). There are approximately 16-18 bolts securing the timing cover. Carefully pry the timing cover away from the engine block using plastic pry tools at designated pry points. Remove the cover and old gasket material. Inspect the crankshaft seal in the timing cover.
   Torque spec

   Timing Cover Bolts18 Nm (14 lb-ft)
5. 5

   Verify and mark timing alignment
   Rotate the crankshaft to Top Dead Center (TDC) for cylinder #1. Verify timing marks on camshaft gear and crankshaft gear align with marks on the engine block and oil pump housing. Use paint or marker to clearly mark the current position of the timing chain on both sprockets. Take multiple reference photos. Install timing pins if available for this engine to lock components in position.
   ⚠️This is the most critical step. Verify timing marks multiple times before proceeding. Incorrect timing will cause severe engine damage.
6. 6

   Remove timing chain tensioner
   Locate the timing chain tensioner on the passenger side of the timing cover area. The tensioner bolt is accessible from the front. Remove the tensioner mounting bolt and carefully extract the tensioner assembly. Note the position and orientation of the tensioner. Inspect the tensioner pad and guide shoes for wear.
   Torque spec

   Tensioner Bolt27 Nm (20 lb-ft)
7. 7

   Inspect timing chain and guides
   With the tensioner removed, inspect the timing chain for stretch, wear, or damage. Check chain guides and wear pads for grooving or excessive wear. Verify the camshaft sprocket bolt is tight. If chain or guides show wear, they should be replaced at this time. Measure chain slack if a dial indicator is available.
   Torque spec

   Camshaft Sprocket Bolt101 Nm (74 lb-ft)
8. 8

   Prepare new tensioner
   Remove the new timing chain tensioner from packaging. The tensioner must be compressed and locked with its retaining pin or clip before installation. Compress the tensioner plunger fully by hand or in a vise (gently), then insert the retaining pin through the body to hold it in the compressed position. Apply a small amount of clean engine oil to the tensioner pad surface.
   ℹ️The tensioner must remain locked with pin/clip during installation. Do not release the pin until instructed.
9. 9

   Install new tensioner
   Position the new compressed and pinned tensioner into its mounting location. Ensure the tensioner pad properly contacts the timing chain guide. Install the new tensioner mounting bolt and tighten to specification. Verify the tensioner is properly seated before torquing. Do NOT remove the retaining pin yet.
   Torque spec

   Tensioner Bolt27 Nm (20 lb-ft)
10. 10

    Release tensioner and verify timing
    Carefully remove the retaining pin or clip from the tensioner, allowing it to apply pressure to the timing chain. Manually rotate the crankshaft two complete revolutions clockwise (viewed from front). Verify that all timing marks realign perfectly at TDC. If marks do not align, do not proceed - disassemble and verify chain position.
    ⚠️If timing marks do not realign after two rotations, the timing is incorrect. Stop immediately and troubleshoot before continuing.
11. 11

    Install new timing cover seal and gasket
    Clean all timing cover and block mating surfaces thoroughly with gasket scraper and solvent. Install new crankshaft front seal into timing cover using appropriate seal driver. Position new timing cover gasket on engine block, using alignment dowels. Apply small beads of RTV silicone to corners where gasket meets oil pan rail.
12. 12

    Install timing cover
    Carefully position timing cover over crankshaft snout and onto engine block, ensuring gasket stays in position. Install all timing cover bolts finger-tight first. Identify 8mm bolts and standard bolts, installing in correct locations. Tighten all bolts in a crossing pattern starting from center and working outward. Tighten 8mm bolts to their specification first, then standard bolts.
    Torque spec

    Timing Cover Bolts18 Nm (14 lb-ft)
13. 13

    Install crankshaft pulley
    Clean crankshaft snout and pulley bore thoroughly. Apply a thin coat of clean engine oil to crankshaft snout. Slide crankshaft pulley onto snout, aligning keyway. Install crankshaft pulley bolt with a small amount of engine oil on threads. Tighten bolt to specification while preventing engine rotation by locking flywheel.
    Torque spec

    Crankshaft Pulley Bolt238 Nm (176 lb-ft)
14. 14

    Reinstall valve cover and accessories
    Install new valve cover gasket onto valve cover. Position valve cover onto cylinder head, ensuring gasket stays in place. Install valve cover bolts and tighten in sequence from center outward to specification. Reinstall all accessories in reverse order of removal: alternator bracket and alternator, A/C compressor, power steering pump and bracket. Reinstall serpentine belt according to routing diagram.
    Torque spec

    Valve Cover Bolts10 Nm (7 lb-ft)
15. 15

    Reinstall cooling system and finalize
    Reinstall cooling fan assembly and fan shroud. Reconnect radiator hoses. Refill cooling system with proper OAT coolant mixture. Refill engine oil to proper level with fresh oil. Remove engine support fixture. Reconnect battery terminals (positive first, then negative). Start engine and verify no leaks. Allow engine to reach operating temperature and check coolant level.

Reassembly

1. Verify all fasteners are torqued to specification before starting engine
2. Double-check that no tools or loose parts remain in engine compartment
3. Ensure all electrical connectors are properly seated and secured
4. Verify serpentine belt is properly routed and tensioned
5. Check that all hoses and lines are reconnected and secured with clamps

Verification

• Start engine and listen for abnormal timing chain noise or rattles
• Verify engine idles smoothly without misfires or rough running
• Check for coolant, oil, or fuel leaks around timing cover and valve cover
• Allow engine to reach full operating temperature and verify cooling system operation
• Test drive vehicle under light load and verify normal engine performance
• Recheck fluid levels after test drive and top off as necessary
• Monitor engine for any unusual noises or vibrations during first 100 miles of operation

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