Head Gaskets - Both

Complete replacement of head gaskets on both cylinder banks of the M275 6.0L V12 BiTurbo engine, requiring removal of intake/exhaust systems, valve covers, timing components, and cylinder heads.

Warnings

Tools required

Parts

• Cylinder head gasket - left bank × 1 — Use OEM specification
• Cylinder head gasket - right bank × 1 — Use OEM specification
• Cylinder head bolt set - both banks × 1 — TTY bolts, use OEM specification
• Valve cover gasket - left × 1 — Use OEM specification
• Valve cover gasket - right × 1 — Use OEM specification
• Intake manifold gasket set × 1 — Use OEM specification
• Exhaust manifold gaskets - both banks × 2 — Use OEM specification
• Timing cover gasket × 1 — Use OEM specification
• Timing chain tensioner seals × 2 — Use OEM specification
• Camshaft cap seals × 1 — Use OEM specification
• VVT solenoid O-rings × 4 — Use OEM specification
• Coolant temperature sensor O-ring × 2 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Thermostat housing gasket × 2 — Use OEM specification
• Oil separator valve seals × 1 — Use OEM specification

Fluids

• Mercedes-Benz Coolant (Blue) — 18 qt
• Mercedes-Benz 229.5 5W-40 — 8.5 qt

Preparation

1. Position vehicle on level surface and engage parking brake
2. Disconnect negative battery terminal and wait 10 minutes for system discharge
3. Relieve fuel system pressure by removing fuel pump fuse and cranking engine briefly
4. Remove engine cover panels and undertray
5. Drain engine coolant completely into appropriate container
6. Drain engine oil and replace oil drain plug with new crush washer
7. Remove both turbochargers and intercooler system (requires separate procedure)
8. Remove air intake system and mass airflow sensors
9. Disconnect all vacuum lines, labeling each for reinstallation
10. Document all electrical connector positions with photos before disconnection
11. Support engine with overhead hoist or engine support bar

Procedure

1. 1

   Remove intake manifold assembly
   Disconnect throttle body connections and fuel rails from both banks. Remove all ignition coils and spark plugs. Unbolt and remove complete intake manifold assembly as a unit. The M275 uses a complex manifold that spans both banks - work carefully to avoid damaging plastic components.
   Torque spec

   Intake Manifold Bolts25 Nm (18 lb-ft)
2. 2

   Remove exhaust manifolds and turbo connections
   Disconnect oxygen sensors from both banks. Remove exhaust manifold heat shields. Unbolt exhaust manifolds from cylinder heads on both left and right banks. Support manifolds carefully as they are removed to avoid stress on remaining turbo connections.
   ⚠Exhaust studs are prone to breaking on this engine. Apply penetrating oil 24 hours before removal if possible. Have replacement studs available.
   Torque spec

   Exhaust Manifold Nuts30 Nm (22 lb-ft)
3. 3

   Remove valve covers and inspect valvetrain
   Disconnect cam position sensors and VVT solenoids from both valve covers. Remove valve cover bolts in reverse of tightening sequence (outside to inside). Carefully lift valve covers and inspect for oil sludge. Clean all surfaces thoroughly. Inspect rocker arms and cam lobes for wear while accessible.
   Torque spec

   Valve Cover Bolts10 Nm (7 lb-ft)

   VVT Solenoid Bolt10 Nm (7 lb-ft)
4. 4

   Lock engine at TDC and secure timing components
   Rotate engine by hand to TDC cylinder 1 using crankshaft pulley bolt. Install crankshaft locking pin through engine block. Install camshaft alignment tools on both banks to lock all four camshafts in position. Verify all timing marks align correctly before proceeding. Mark timing chain to sprocket positions with paint marker.
   ⚠️Do NOT proceed if timing marks do not align perfectly. Incorrect timing will destroy engine upon startup.
   Torque spec

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)
5. 5

   Remove timing chain tensioners and guides
   Remove timing chain tensioner bolts from both banks. Use proper pin or clip to compress tensioners before removal. Remove timing chain guides while keeping chains supported with wire or dedicated holding tool. Do not allow chains to fall into engine cavity.
   ⚠Support timing chains with wire to prevent them from falling. Retrieving a dropped chain requires complete front cover removal.
   Torque spec

   Timing Chain Tensioner Bolt25 Nm (18 lb-ft)
6. 6

   Remove camshaft sprockets
   Hold each camshaft with wrench on hex section while removing camshaft sprocket bolts. Remove all four camshaft sprockets (two per bank). Keep sprockets with their respective chains using wire ties. Mark left and right bank components to avoid mixing during reassembly.
   Torque spec

   Camshaft Sprocket Bolt80 Nm (59 lb-ft)
7. 7

   Remove camshafts from both banks
   Remove camshaft cap bolts in reverse sequence (outward from center) in multiple passes, loosening 1/4 turn at a time to prevent camshaft distortion. Remove camshaft caps, keeping them in order with labels. Carefully lift camshafts from heads and store in protective covers. Inspect cam journals for scoring.
   ⚠Camshaft cap bolts must be loosened gradually in correct sequence. Uneven loosening can bend camshafts or crack caps.
   Torque spec

   Camshaft Cap Bolts14 Nm (10 lb-ft)
8. 8

   Remove rocker arms and hydraulic lifters
   Remove all rocker arm bolts and lift rocker arms from heads. Keep rocker arms organized by cylinder number and bank. Remove hydraulic lifters using magnetic tool, storing them upright in numbered holders to maintain original positions. Inspect all lifter faces for wear or pitting.
   Torque spec

   Rocker Arm Bolts30 Nm (22 lb-ft)
9. 9

   Disconnect remaining cylinder head connections
   Disconnect coolant temperature sensors from both heads. Remove coolant crossover pipes between banks. Disconnect ground straps from heads. Remove any remaining brackets, sensors, or mounting points attached to cylinder heads. Verify all connections are free.
   Torque spec

   Sensor Mounting Bolts10 Nm (7 lb-ft)
10. 10

    Remove cylinder head bolts and lift heads
    Remove cylinder head bolts in reverse of tightening sequence (outside to inside pattern) in multiple stages. Once all bolts are removed, use pry points to break gasket seal - never pry between head and block surfaces. Attach lifting fixture to cylinder head and use hoist to carefully lift each head vertically. Immediately cover exposed cylinders with clean rags.
    ⚠️Each cylinder head weighs approximately 85 lbs. Use proper lifting equipment and get assistance. Never attempt to lift heads manually.
    Torque spec

    Cylinder Head Bolts119 Nm (88 lb-ft)
11. 11

    Clean and inspect all mating surfaces
    Carefully remove all old gasket material from block and head surfaces using plastic scrapers only. Never use metal scrapers that could gouge aluminum surfaces. Clean with brake cleaner and lint-free cloths. Inspect cylinder head surfaces with straightedge and feeler gauge - maximum warpage is 0.1mm. Send heads for professional resurfacing if needed. Check block deck for warpage as well.
    ⚠Any debris left on mating surfaces will cause immediate head gasket failure. Clean meticulously and verify with bright light.
12. 12

    Install new head gaskets and position heads
    Verify block surfaces are clean and dry. Install new head gaskets on block, ensuring left and right gaskets are correct and properly oriented per markings. Dowel pins should locate gaskets precisely. Carefully lower cylinder heads onto block using hoist, aligning with dowel pins. Do not slide heads across gaskets.
    ⚠Head gaskets are NOT interchangeable between banks. Verify correct left/right orientation before installation.
13. 13

    Install and torque cylinder head bolts
    Install new TTY cylinder head bolts (never reuse old bolts). Hand-thread all bolts first to verify proper thread engagement. Torque bolts to 119 Nm (88 lb-ft) in correct sequence from center outward. Then apply additional angle torque as specified (typically 90° + 90° in two stages). Use angle gauge to ensure precise angle application. Follow exact Mercedes-Benz tightening sequence diagram.
    ⚠️Head bolts are torque-to-yield and MUST be replaced. Angle torque must be applied precisely - over-torquing will yield bolts beyond specification.
    Torque spec

    Cylinder Head Bolts119 Nm (88 lb-ft)
14. 14

    Reinstall lifters, rocker arms, and camshafts
    Install hydraulic lifters in their original positions, or use new lifters if replacing. Oil all camshaft journals and install camshafts in correct positions (intake/exhaust, left/right bank). Position rocker arms and install bolts with cam lobes pointing away from rockers to prevent valve interference. Torque rocker arm bolts to specification. Install camshaft caps in original positions and torque cap bolts in sequence from center outward in multiple passes.
    ⚠Camshaft caps are numbered and position-specific. Installing caps in wrong positions will cause immediate engine failure.
    Torque spec

    Rocker Arm Bolts30 Nm (22 lb-ft)

    Camshaft Cap Bolts14 Nm (10 lb-ft)
15. 15

    Reinstall timing components and verify alignment
    Install camshaft sprockets with timing marks aligned to previous paint marks and chains. Torque sprocket bolts to specification while holding camshafts. Install timing chain guides and tensioners with new seals. Verify crankshaft locking pin is still engaged. Remove camshaft alignment tools and manually rotate engine two complete revolutions. Reinstall alignment tools - they should slide in freely at TDC if timing is correct. Remove all locking tools before final reassembly.
    ⚠️After rotating engine two revolutions, alignment tools MUST fit freely. If not, timing is incorrect and engine must not be started.
    Torque spec

    Camshaft Sprocket Bolt80 Nm (59 lb-ft)

    Timing Chain Tensioner Bolt25 Nm (18 lb-ft)

Reassembly

1. Install valve covers with new gaskets, torquing bolts in sequence from center outward
2. Reinstall exhaust manifolds with new gaskets, torquing nuts evenly to specification
3. Reinstall intake manifold with new gaskets, connecting all vacuum lines and electrical connectors per documentation
4. Reinstall turbochargers and intercooler system with new gaskets and seals
5. Reinstall all sensors, ensuring VVT solenoids and cam position sensors are properly torqued
6. Install new spark plugs and ignition coils
7. Reconnect all coolant hoses and fill cooling system with Mercedes-Benz Blue coolant to proper level
8. Fill engine with fresh Mercedes-Benz 229.5 5W-40 oil to proper level
9. Reconnect battery negative terminal
10. Reinstall engine covers and undertray

Verification

• Prime oil system by cranking engine with fuel pump fuse removed until oil pressure builds
• Start engine and verify immediate oil pressure indication
• Check for coolant, oil, or exhaust leaks while engine runs at idle
• Verify smooth idle with no misfires or unusual noises from valvetrain
• Allow engine to reach operating temperature and verify cooling fans cycle properly
• Connect Mercedes-Benz STAR diagnostic system and verify no fault codes related to camshaft timing
• Perform camshaft adjustment verification procedure using STAR system
• Road test vehicle under light load, monitoring coolant temperature and oil pressure
• Re-check all fluid levels after test drive and inspect for any new leaks
• Recommend 500-mile service to re-torque cylinder head bolts if specified by manufacturer (verify in service manual)

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