Timing Chain Kit

Complete replacement of timing chain, guides, tensioners, and related components on the M275 6.0L V12 BiTurbo engine. This is an intensive procedure requiring engine mount manipulation and removal of major engine covers.

Warnings

Tools required

Parts

• Timing chain kit (includes chains, guides, tensioners) × 1 — Use Mercedes-Benz OEM timing chain kit for M275 engine
• Crankshaft front seal × 1 — Use OEM specification
• Camshaft seals (front) × 4 — Use OEM specification
• Timing cover gasket/seal kit × 1 — Use OEM specification
• Valve cover gaskets (both banks) × 2 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Engine oil 5W-40 Mercedes-Benz 229.5 × 1 — Use OEM specification
• Oil filter × 1 — Use OEM specification
• Coolant (Mercedes-Benz Blue) × 1 — Use OEM specification

Fluids

• Mercedes-Benz 229.5 5W-40 — 8.5 qt
• Mercedes-Benz Coolant (Blue) — 2 qt

Preparation

1. Disconnect negative battery terminal and wait 10 minutes for system discharge
2. Raise vehicle on lift or secure on jack stands at manufacturer specified lift points
3. Drain engine oil completely and remove oil filter
4. Drain coolant from radiator and engine block drain points
5. Remove engine cover and beauty covers
6. Remove air intake system, airbox, and mass airflow sensors
7. Photograph and label all wiring harness connections for both cylinder banks
8. Remove serpentine belt and accessory drive components (alternator, AC compressor, power steering pump)
9. Support engine from above using engine support fixture with load leveler capability

Procedure

1. 1

   Remove upper engine components and prepare access
   Remove intake manifold assembly, fuel rails, and ignition coils from both cylinder banks. Remove both valve covers and set aside on clean surface. Disconnect coolant pipes and heater hoses that obstruct access to timing cover. Remove throttle body and any remaining components blocking access to front of engine.
2. 2

   Support engine and remove front mount
   With engine support fixture engaged, slightly raise engine to unload front engine mount. Remove front engine mount bolts and the mount assembly. This provides necessary clearance to remove timing cover. Adjust engine position as needed for optimal access.
   ⚠Ensure engine support is secure before removing mount. Engine must not shift during timing work.
3. 3

   Remove crankshaft pulley and harmonic balancer
   Lock crankshaft using appropriate holding tool. Remove crankshaft pulley bolt using breaker bar or impact wrench. Use harmonic balancer puller to remove pulley from crankshaft snout. Inspect keyway for damage.
   ⚠Never use a jaw-type puller that grips outer edge of balancer. Must use hub-mounted puller to prevent damage.
   Torque spec

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)
4. 4

   Remove timing cover
   Remove all timing cover bolts, noting their locations as they are different lengths. Carefully remove timing cover, being mindful of locating dowels. Clean all gasket surfaces thoroughly using plastic scraper. Inspect for cracks or warping.
   Torque spec

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

   Rotate engine to TDC and verify timing marks
   Rotate crankshaft clockwise (viewed from front) until cylinder 1 is at TDC compression stroke. Install crankshaft locking pin through timing cover opening. Verify camshaft timing marks on both banks align with their respective marks on cylinder heads. Install camshaft locking tools to secure all four camshafts in correct position.
   ⚠️All timing marks must align exactly. If marks do not align perfectly, investigate cause before proceeding. Do not force locking tools.
6. 6

   Remove timing chain tensioners and guides
   Starting with left bank, remove timing chain tensioner by first removing tensioner bolt. Carefully extract tensioner assembly. Remove timing chain guide bolts and guides. Repeat procedure for right bank. Inspect all components for wear, scoring, or cracks.
   Torque spec

   Tensioner Bolt27 Nm (20 lb-ft)

   Guide Bolts33 Nm (24 lb-ft)
7. 7

   Remove camshaft sprockets and timing chains
   With camshafts locked in position, hold each camshaft on the hex portion using appropriate wrench. Remove camshaft sprocket bolts from all four camshafts. Remove cam phasers if equipped by removing cam phaser bolts. Lift timing chains off crankshaft sprocket and remove chains from engine. Mark chains left and right if reusing.
   Torque spec

   Camshaft Sprocket Bolt80 Nm (59 lb-ft)

   Cam Phaser Bolt65 Nm (48 lb-ft)
8. 8

   Remove and inspect idler sprockets
   Remove timing chain idler sprocket bolts and remove idler sprockets. Inspect sprockets for wear on teeth, worn bearings, or play. Replace if any wear is evident. Clean mounting surfaces thoroughly.
   Torque spec

   Timing Chain Idler Sprocket25 Nm (18 lb-ft)
9. 9

   Install new idler sprockets and guides
   Install new or inspected idler sprockets and torque bolts to specification. Install new timing chain guides and torque guide bolts to specification. Ensure all guide surfaces are clean and bolts are properly seated.
   Torque spec

   Timing Chain Idler Sprocket25 Nm (18 lb-ft)

   Guide Bolts33 Nm (24 lb-ft)
10. 10

    Install new timing chains
    With crankshaft still locked at TDC, route new timing chains around crankshaft sprocket and up through both banks. Ensure chains are properly seated in all guide channels. Verify chain direction if marked. Do not allow chains to fall into lower engine area.
    ℹ️Some timing chain kits include colored links for alignment. Align colored links with marks on sprockets per manufacturer instructions.
11. 11

    Install camshaft sprockets and cam phasers
    With camshafts still locked, install cam phasers (if equipped) onto camshaft snouts, applying medium-strength threadlocker to bolts. Install camshaft sprockets over timing chains, aligning timing marks. Hold camshaft hex with wrench and torque sprocket bolts to specification. Torque cam phaser bolts to specification.
    ⚠Do not allow camshafts to rotate during installation. Verify locking tools remain engaged throughout.
    Torque spec

    Camshaft Sprocket Bolt80 Nm (59 lb-ft)

    Cam Phaser Bolt65 Nm (48 lb-ft)
12. 12

    Prepare and install timing chain tensioners
    Compress new timing chain tensioners fully and install locking pins or clips to hold them in compressed position. Install tensioners into their bores and torque tensioner bolts to specification. Do not remove locking pins yet.
    ⚠Tensioners must remain locked during installation. Premature release will prevent proper installation.
    Torque spec

    Tensioner Bolt27 Nm (20 lb-ft)
13. 13

    Verify timing alignment and release tensioners
    Triple-check all timing marks are correctly aligned with camshaft and crankshaft locking tools still installed. Verify chains are properly seated on all sprockets. Carefully remove tensioner locking pins from both tensioners simultaneously. Remove camshaft and crankshaft locking tools. Manually rotate crankshaft two complete revolutions clockwise. Reinstall locking tools to verify timing marks still align perfectly.
    ⚠️This is the critical verification step. If timing marks do not realign after two rotations, timing is incorrect. Disassemble and repeat installation.
14. 14

    Install timing cover with new seals
    Install new crankshaft front seal into timing cover. Apply thin bead of RTV silicone to timing cover gasket surfaces per manufacturer specifications. Position new timing cover gasket and carefully install timing cover, ensuring alignment dowels engage properly. Install timing cover bolts in sequence: 6mm bolts first, then 8mm bolts, then 10mm bolts, torquing each size to respective specifications.
    ℹ️Allow RTV silicone to cure for minimum time specified by manufacturer before adding oil.
    Torque spec

    Timing Cover Bolts18 Nm (14 lb-ft)
15. 15

    Install crankshaft pulley and complete reassembly
    Clean crankshaft snout and pulley hub thoroughly. Install harmonic balancer onto crankshaft, ensuring keyway aligns. Install new crankshaft pulley bolt (if TTY type) and torque to specification. Install front engine mount and remove engine support. Reinstall valve covers with new gaskets, torquing bolts in sequence to specification. Reinstall all remaining components in reverse order of removal.
    Torque spec

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)

    Valve Cover Bolts10 Nm (7 lb-ft)

Reassembly

1. Reinstall all coolant hoses and pipes, replacing any damaged clamps
2. Install new oil filter and drain plug with new crush washer torqued to specification
3. Reinstall intake manifold, fuel rails, and ignition coils
4. Reinstall all accessory drive components and serpentine belt with proper tension
5. Refill engine with 8.5 quarts of Mercedes-Benz 229.5 5W-40 engine oil
6. Refill cooling system with Mercedes-Benz Blue coolant and bleed air from system
7. Reconnect all electrical connectors and vacuum lines per photos taken during disassembly
8. Reinstall air intake system and engine covers
9. Reconnect battery negative terminal

Verification

• Before starting engine, manually rotate crankshaft one full revolution to verify no interference or binding
• Prime oil system by cranking engine with fuel system disabled until oil pressure builds
• Start engine and verify no unusual noises from timing chain area
• Check for oil leaks around timing cover, valve covers, and drain plug
• Check for coolant leaks at all disturbed connections
• Allow engine to reach operating temperature and verify proper idle quality on both banks
• Monitor engine for any timing-related fault codes using diagnostic scanner
• Road test vehicle under light load and verify smooth operation across RPM range
• Recheck oil level after test drive and top off if necessary
• Verify no timing chain rattle at cold start or under acceleration

Related trouble codes on this vehicle

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