Main Bearings

Complete removal and replacement of all main bearing shells in the 6.0L V12 engine, requiring engine removal from vehicle, disassembly of rotating assembly, and precise reassembly with torque-to-yield fasteners.

Warnings

Tools required

Parts

• Main bearing shell set (upper and lower, all positions) × 1 — Use OEM Aston Martin specification - typically 7 bearing positions
• Thrust bearing set (if separate from main bearings) × 1 — Use OEM specification
• Main bearing cap bolts (TTY - do not reuse) × 14 — Use OEM specification
• Oil pan gasket or RTV sealant × 1 — Use OEM specification
• Oil filter cartridge × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Engine oil (5W-30) × 11 — OEM approved specification
• Coolant (OAT 50/50 premix) × 11 — OEM approved specification
• Rear main seal (if replacement required) × 1 — Use OEM specification
• Oil pump pickup tube O-ring × 1 — Use OEM specification
• Transmission input shaft seal (inspect and replace if needed) × 1 — Use OEM specification
• Engine mount fasteners (inspect and replace if needed) × 1 — Use OEM specification

Fluids

• 5W-30 engine oil — 10.5 qt
• OAT 50/50 coolant — 10.5 qt

Preparation

1. Position vehicle on level surface with adequate clearance for engine hoist and transmission jack operation
2. Disconnect negative battery terminal and isolate cable
3. Remove engine cover panels from top of engine bay
4. Drain engine oil completely and remove oil filter
5. Drain engine coolant from radiator and block drain points
6. Relieve fuel system pressure by removing fuel pump fuse and cranking engine until it stalls
7. Document all electrical connector positions with photos before disconnection
8. Obtain factory service manual with main bearing cap torque sequence and crankshaft journal specifications
9. Prepare clean workspace for engine stand mounting and disassembly
10. Label all fasteners and components during removal using organized storage trays

Procedure

1. 1

   Remove engine from vehicle
   Remove hood by disconnecting gas struts and removing hinge bolts (typically 4 per side). Disconnect all engine electrical connectors including alternator, starter, ignition coils, sensors, and engine harness main connector. Disconnect throttle body connections and vacuum lines. Remove intake air system from throttle body to air filter housing. Disconnect fuel supply and return lines using appropriate disconnect tools. Disconnect all coolant hoses from engine including radiator hoses, heater hoses, and bypass hoses. Disconnect A/C compressor lines at compressor and secure compressor to body without disconnecting from vehicle (3-4 mounting bolts). Remove drive belts. Support the driveline as required. Separate the engine from the torque tube at the factory-specified disconnect point (the DB9 uses a rear transaxle connected by a torque tube, not an engine-mounted bellhousing) per the service manual. Disconnect exhaust system at manifold/downpipe flanges (verify exact fastener count against the Aston Martin service manual). Remove front motor mount through-bolts. Attach engine hoist with chain or strap to factory lift points on cylinder heads. Apply slight upward tension to verify balance. Remove any remaining ground straps or connections. Carefully lift engine while separating it from the torque tube/driveplate coupling (the DB9 uses a rear transaxle driven through a torque tube, not a transmission bolted directly to the engine). Tilt engine as needed to clear chassis rails and remove from vehicle. Mount engine securely to engine stand using bellhousing bolt holes. Note: Carefully lift engine while clearing the flexplate/drive plate and torque tube coupling per the service manual.
2. 2

   Remove external engine accessories
   With engine on stand, remove alternator mounting bolts and alternator. Remove power steering pump (if equipped) and secure aside without disconnecting lines. Remove A/C compressor mounting bracket. Remove starter motor mounting bolts and starter. Remove coolant housing and thermostat assembly. Remove engine wiring harness completely, documenting all bracket locations. Remove ignition coil packs and spark plugs from all 12 cylinders. Remove fuel rail assembly with injectors attached. Remove throttle body and intake manifold assembly (this will require removing multiple sections on this V12 - upper plenum, lower runners). Remove valve covers from both cylinder banks. Document rocker arm and lifter positions if disassembly is required for clearance.
3. 3

   Remove timing chains and front covers
   Rotate engine to TDC position on cylinder #1 (align timing marks on crankshaft and camshafts). Lock crankshaft in position using appropriate holding tool. Remove crankshaft pulley bolt (this will be a high-torque fastener requiring breaker bar). Remove harmonic balancer using appropriate puller. Remove front timing cover bolts (multiple sizes, document locations) and remove timing cover. Remove primary timing chain tensioner(s). Remove timing chain guides. Remove primary timing chain(s) from crankshaft sprocket and camshaft sprockets. On this V12, there are two cylinder banks with separate timing systems - remove chains from both banks. Remove camshaft sprockets if needed for clearance. Mark and document all timing component positions with photos.
4. 4

   Remove cylinder heads
   Remove cylinder head bolts in reverse of tightening sequence (consult service manual for proper sequence). This V12 uses the head bolt count specified in the factory manual (verify exact number of cylinder head bolts per head against the Aston Martin service manual). Carefully lift cylinder heads from block using appropriate lifting method - these aluminum heads are heavy. Place heads on padded surface to prevent damage. Remove and discard cylinder head gaskets. Inspect cylinder head bolt holes in block for debris or thread damage. Cover exposed cylinders with clean shop towels to prevent debris entry. Note: Cylinder head removal is NOT required for main bearing service. Main bearing caps are accessed from below after oil pan removal. If heads are not being serviced, skip head removal entirely. Note: This V12 uses a specific number of cylinder head bolts per head - consult the factory service manual for the exact count before removal. Note: Note: Cylinder head removal is not required to access the main bearing caps, which are accessed from below after oil pan removal. Head removal here is only performed if required for engine stand mounting or additional inspection; main bearing service is performed from the bottom end of the block. Note: Remove the cylinder head bolts per head (verify exact bolt count and pattern in the factory service manual for this engine). Note: Note: On this platform, main bearing caps are accessed from below after oil pan removal. Cylinder head removal is NOT required to access the main bearings; perform head removal only if separately required for crankshaft or engine servicing.
5. 5

   Remove oil pan and oil pump
   Remove oil pan bolts in crisscross pattern working from ends toward center. Carefully separate oil pan from block using plastic pry tools at designated pry points - do not damage sealing surfaces. Remove oil pan and gasket. Remove oil pump pickup tube mounting bolt and remove pickup tube with O-ring. Remove oil pump mounting bolts (typically 3-4 bolts) and remove oil pump assembly from front of crankshaft. Inspect oil pump drive mechanism for wear. Clean all oil passages in block using solvent and compressed air.
6. 6

   Mark and document main bearing cap positions
   Before removing any main bearing caps, use permanent marker or stamping punch to mark each cap with its position number (front to rear per the factory service manual main bearing count) and orientation arrow pointing toward front of engine. The factory may have already marked caps, but verify all markings are clear and legible. Take photographs of cap positions and orientations. Note: Main bearing caps are machined as matched pairs with the block and are NOT interchangeable. Installing caps in wrong positions will cause immediate bearing failure and crankshaft destruction.
7. 7

   Remove connecting rod caps and pistons
   Rotate crankshaft to position each connecting rod at bottom dead center (BDC) for access. Mark each connecting rod and cap with cylinder number and orientation before removal. Remove connecting rod cap bolts and caps. Push pistons up and out of bores from below. Install rod caps back onto rods loosely to prevent mixing. Store piston/rod assemblies in order with cylinder numbers clearly marked. This step provides clearance to remove crankshaft and prevents piston/ring damage during crankshaft removal.
8. 8

   Remove main bearing caps and crankshaft
   Beginning with the center main bearing cap, remove the main bearing cap bolts (verify exact number of bolts per cap, including any side/cross bolts, in the factory service manual). These are TTY bolts and must be discarded - do not reuse. Carefully remove the main bearing cap and lower bearing shell. Continue removing caps working alternately outward from center per the factory service manual sequence (verify exact loosening order and whether this engine uses a one-piece main bearing ladder/bedplate before proceeding). Store each cap/bedplate with its bearing shell and mark shells as 'removed' with position number. NOTE: Verify whether this engine uses individual main bearing caps or a one-piece main bearing ladder/bedplate before proceeding, as the removal method and bolt pattern differ significantly. Once all caps are removed, carefully lift crankshaft straight up out of block. This crankshaft is heavy - use appropriate lifting equipment or a two-person lift (verify exact crankshaft weight if a lifting figure is needed). Place crankshaft on padded surface. Remove upper main bearing shells from block and mark each with position number. Identify thrust bearing position (typically center or rear position) and mark thrust bearing shells separately. Note: Beginning with the center main bearing position, loosen and remove the main bearing cap/ladder bolts per the factory service manual (verify exact bolt count and whether a one-piece main bearing ladder/bedplate with cross-bolts is used on this engine).
9. 9

   Inspect and measure crankshaft journals
   Clean all crankshaft main journals thoroughly with solvent and lint-free towels. Inspect journals for scoring, heat discoloration, or excessive wear. Using outside micrometer, measure each main journal diameter at multiple points (top, bottom, and 45-degree positions) and at multiple locations along journal length. Record all measurements. Compare measurements to factory specifications (obtain exact nominal main journal diameter and out-of-round tolerance from the Aston Martin factory service manual — do not rely on assumed values). If journals are out-of-specification, crankshaft must be reground or replaced. Inspect oil passages in crankshaft for blockage using compressed air and wire brush. Ensure all passages are clear and clean. Note: Compare measurements to factory specifications for main journal nominal diameter and out-of-round tolerance as listed in the Aston Martin service manual (do not rely on assumed values). Note: Compare measurements to factory specifications for main journal diameter and out-of-round tolerance as listed in the service manual for this engine.
10. 10

    Inspect block bearing bores and prepare surfaces
    Clean all main bearing saddles in block thoroughly with solvent and lint-free towels. Inspect bearing bores for damage, scoring, or distortion. Using telescoping bore gauge and outside micrometer, measure each bearing bore diameter with caps installed (torqued to specification WITHOUT bearings installed). This establishes the true bore diameter. Record measurements for each position. Check block deck surfaces for warpage using precision straightedge. Clean all oil passages in block using solvent spray and compressed air. Ensure oil return passages from main bearing saddles are clear. Inspect main bearing cap bolt holes for thread damage and chase threads if necessary with appropriate tap.
11. 11

    Install new main bearing shells and perform clearance check
    Install new upper bearing shells into block saddles - shells should snap into place with tab engaging notch in saddle. Ensure shells are fully seated with no gaps. Install thrust bearing halves in correct position (verify orientation with service manual). Wipe bearing surfaces with clean, lint-free towel - surfaces must be completely dry and oil-free for Plastigage measurement. Place strip of appropriate Plastigage (0.001-0.003 inch range) lengthwise on each main journal of crankshaft. Carefully lower crankshaft into block bearing saddles. Install lower bearing shells into main bearing caps ensuring proper orientation and full seating. Install main bearing caps in correct positions with orientation arrows toward front of engine. Install NEW main bearing cap bolts and hand-tighten only. Using torque sequence specified in service manual (typically starting at center and working outward), torque main bearing cap bolts to the factory-specified Plastigage measurement torque (obtain exact value from the Aston Martin service manual) in sequence. DO NOT rotate crankshaft. Immediately remove main bearing caps in reverse order without rotating crankshaft. Measure crushed Plastigage width using gauge on Plastigage package. Width indicates bearing clearance: narrower crush indicates larger clearance. Record clearance for each bearing position. Compare measured clearance to the factory-specified main bearing clearance range (obtain exact values from the Aston Martin service manual — do not rely on assumed values). If any clearances are out of specification, determine cause (incorrect bearing size, damaged journals, damaged bores) and correct before proceeding. Note: torque main bearing cap bolts to the factory-specified first-stage torque in sequence (verify exact value in the Aston Martin service manual before Plastigage check) Note: Using torque sequence specified in service manual (typically starting at center and working outward), torque main bearing cap bolts to the factory-specified main bearing cap torque in sequence.
    Torque spec

    Main Bearing Cap Bolts43 Nm (32 lb-ft)
12. 12

    Perform final main bearing installation
    Once clearances are verified acceptable, remove crankshaft and all bearing shells. Clean all Plastigage residue from crankshaft journals and bearing shells using solvent and lint-free towels. Reinstall upper bearing shells in block saddles. Lubricate each upper bearing shell generously with fresh engine oil (same specification as will be used for fill). Apply oil to entire bearing surface. Lubricate all crankshaft main journals with engine oil. Carefully lower crankshaft into bearing saddles. Install lower bearing shells in main bearing caps and lubricate with engine oil. Apply thin bead of RTV silicone (Loctite 5900 or equivalent) to rear main bearing cap at block mating surface corners (small bead only at side seals). Install main bearing caps in correct positions with orientation verified. Install NEW main bearing cap bolts finger-tight. Following factory torque sequence diagram, torque main bearing cap bolts in the stages specified by the Aston Martin service manual (obtain exact per-stage torque values and final torque-angle degrees from the manual — do not use assumed values). Verify crankshaft rotates freely by hand after installation - there should be slight drag from bearings but no binding or hard spots. If crankshaft binds, determine cause immediately (misaligned cap, incorrect bearing, debris). Note: torque main bearing cap bolts in the factory-specified stages (initial torque pass(es) followed by the specified torque-angle) exactly as listed in the Aston Martin service manual - do not use assumed values Note: Following factory torque sequence diagram, torque main bearing cap bolts in the factory-specified stages (initial snug torque, intermediate torque, then final torque-angle), using the exact values and angle from the service manual for this engine. Note: after initial torque to the factory-specified first-stage value
    Torque spec

    Main Bearing Cap Bolts43 Nm (32 lb-ft)
13. 13

    Check crankshaft end play
    Mount dial indicator on engine block with indicator plunger contacting crankshaft flange or thrust surface. Using appropriate pry bar, move crankshaft fully forward and zero dial indicator. Pry crankshaft fully rearward and record end play reading on dial indicator. Compare end play to the factory-specified crankshaft end play range (obtain exact values from the Aston Martin service manual — do not rely on assumed values). If end play is excessive, verify thrust bearing installation and orientation. If end play is insufficient, verify correct thrust bearing part number and installation. End play must be within specification or thrust bearing failure will occur.
14. 14

    Reinstall pistons and connecting rods
    Clean all cylinder bores with solvent and wipe dry. Lubricate cylinder walls with engine oil. Install ring compressor on piston #1 and compress rings. Ensure connecting rod bearing shells are installed and lubricated. Lower piston/rod assembly into cylinder #1 with connecting rod orientation marks toward correct position. Use hammer handle to gently tap piston down through ring compressor into bore. Rotate crankshaft to position rod journal at BDC. Lubricate rod bearing and journal. Install connecting rod cap in correct orientation and torque rod bolts to specification. Verify rod has proper side clearance on crankshaft journal and rotates freely. Repeat for all 12 cylinders in sequence. Verify crankshaft still rotates freely after all rods are installed.
15. 15

    Reinstall oil pump and oil pan
    Install new O-ring on oil pump pickup tube. Install pickup tube into block and torque mounting bolt to the factory-specified value (verify in Aston Martin service manual). Install oil pump per factory procedure with new O-ring or gasket as required (verify oil pump type and mounting location against the Aston Martin service manual). Torque oil pump mounting bolts to specification. Prime oil pump by filling with clean engine oil before installation if possible. Clean oil pan and block mating surfaces thoroughly with solvent - surfaces must be completely clean and dry. Install new oil pan gasket or apply RTV silicone bead as specified by manufacturer (if RTV is specified, apply continuous 3-4mm bead around entire pan perimeter and around all bolt holes). Install oil pan and start all bolts finger-tight. Following tightening sequence (typically starting at center and working outward in crisscross pattern), torque oil pan bolts to the factory-specified value (verify in the Aston Martin service manual). If RTV was used, allow appropriate cure time before filling with oil. Note: torque oil pan bolts to the factory-specified value (verify in Aston Martin service manual). Note: Install pickup tube into block and torque mounting bolt to the factory-specified value (verify in the Aston Martin service manual).
    Torque spec

    Oil Pan Bolt12 Nm (9 lb-ft)

    Oil Pump Pickup Tube12 Nm (9 lb-ft)
16. 16

    Reinstall cylinder heads
    Clean cylinder head and block mating surfaces thoroughly - surfaces must be free of any old gasket material, oil, or debris. Install new cylinder head gaskets in correct orientation (note front/rear marking and top/bottom orientation). Carefully lower cylinder heads onto block, aligning dowel pins. Install new cylinder head bolts (if TTY type) or clean and inspect reusable bolts. Following cylinder head torque sequence in service manual, torque head bolts in multiple passes to final specification plus angle if required. Typical sequence is 3-4 passes increasing torque each pass, with final angle torque. Install valve train components if removed.
17. 17

    Reinstall timing system
    Install camshaft sprockets if removed. Rotate crankshaft to TDC position for cylinder #1. Align all timing marks per service manual - crankshaft mark, camshaft marks on both banks. Install timing chains on both banks ensuring marks are aligned. Install chain guides and tensioners. Verify timing mark alignment is maintained. Lock tensioners in place. Install front timing cover with new gasket or RTV as specified. Install harmonic balancer onto crankshaft ensuring keyway is properly aligned. Install crankshaft pulley bolt and torque to factory specification (obtain exact torque and any torque-angle requirement from the Aston Martin service manual). Rotate crankshaft two complete revolutions by hand and verify all timing marks realign correctly. This confirms proper timing installation. Note: Install crankshaft pulley bolt and torque to the factory specification, including any torque-angle stage (verify exact specification and whether the bolt is single-use TTY in the Aston Martin service manual). Note: Install crankshaft pulley bolt and torque to the factory specification (verify exact torque and whether a torque-angle step applies for this fastener).
18. 18

    Reinstall external accessories and components
    Install valve covers with new gaskets. Install intake manifold assembly with new gaskets in reverse order of removal. Install throttle body with new gasket. Install fuel rail and injectors. Install all ignition coils and spark plugs (torque plugs to specification). Install engine wiring harness and reconnect all sensors and connectors. Install starter motor and torque bolts. Install alternator and mounting brackets. Install power steering pump. Install A/C compressor bracket and compressor. Install all coolant housings and thermostat with new gaskets/O-rings. Install drive belts and adjust tension.
19. 19

    Reinstall engine in vehicle
    Attach engine hoist to engine using factory lift points. Carefully lower engine into engine bay, aligning motor mounts and guiding transmission input shaft into bellhousing (or aligning flexplate to torque converter if automatic). Install motor mount through-bolts and torque to specification. Install all transmission-to-engine bellhousing bolts and torque to the factory-specified value (verify count and torque in the Aston Martin service manual) in crisscross pattern. Remove transmission jack. Reconnect exhaust system at manifold flanges with new gaskets. Reconnect A/C compressor lines with new O-rings if disconnected. Install all coolant hoses. Reconnect all fuel lines. Reconnect all electrical connectors to engine harness. Install intake air system from throttle body to air filter. Reconnect throttle linkage and vacuum lines. Install hood and align for proper fit. Note: Install all transmission/torque-tube-to-engine bolts and torque to the factory-specified value in the correct pattern (verify in the Aston Martin service manual). Note: Install all transmission/torque-tube-to-engine bolts and torque to the factory specification in a crisscross pattern (verify exact torque for the DB9 rear-transaxle driveline configuration).
    Torque spec

    Transmission-to-Engine Bolts45 Nm (33 lb-ft)
20. 20

    Fill fluids and perform initial startup
    Install new oil filter cartridge. Install oil drain plug with new crush washer and torque to the factory-specified value (verify in Aston Martin service manual). Fill engine with the factory-specified quantity and grade of engine oil (verify exact capacity and oil specification in the Aston Martin service manual), or until dipstick shows full on a level surface. Fill cooling system with the factory-specified quantity and type of coolant (verify exact capacity and coolant specification in the Aston Martin service manual) through radiator and reservoir. Reconnect battery negative terminal. Perform pre-start checks: verify all electrical connectors are secure, verify all hoses are connected, verify no tools or parts are left in engine bay, verify all fluids are filled. Turn ignition to ON position without starting and verify no warning lights indicate problems. Disable both the ignition and fuel injection per the factory procedure (remove the appropriate fuel pump/injector and ignition supply) and crank engine in short bursts to build oil pressure - oil pressure indication should appear/light should go out. Reinstall ignition fuse. Start engine and immediately verify oil pressure indication. Listen for any abnormal noises - main bearing noise is a deep knocking that increases with RPM. Allow engine to idle and warm to operating temperature. Monitor for leaks at oil pan, timing cover, cylinder heads, and all connection points. Verify coolant circulation and proper temperature rise. Note: Disable fuel and ignition per the factory crank-no-start procedure (e.g., remove the fuel pump fuse/relay and ignition as specified by Aston Martin) and crank engine in short bursts to build oil pressure - oil pressure light should go out. Note: Fill engine with the factory-specified oil quantity and viscosity grade (verify exact capacity and grade in the Aston Martin service manual), or until dipstick shows full on a level surface. Note: Fill cooling system with the factory-specified coolant type and quantity (verify exact capacity and coolant specification in the Aston Martin service manual) through radiator and reservoir. Note: Fill engine with the factory-specified engine oil grade and capacity (verify exact AM-approved specification and quantity in the service manual), or until the dipstick shows full on a level surface. Note: verify oil pressure reaches normal specification within 5-10 seconds of startup (verify exact normal oil pressure range for this engine in the Aston Martin service manual)
    Torque spec

    Oil Drain Plug25 Nm (18 lb-ft)

Reassembly

1. All reassembly steps are included in the main procedure steps above
2. Torque all fasteners to specifications using proper sequence as documented in factory service manual
3. Replace all TTY (torque-to-yield) fasteners including main bearing cap bolts and cylinder head bolts
4. Use new gaskets and seals throughout reassembly
5. Verify crankshaft rotates freely after main bearing installation and after connecting rod installation
6. Double-check all timing marks align correctly after timing chain installation and after rotating crankshaft two complete revolutions

Verification

• Verify engine starts and runs smoothly without any knocking, ticking, or abnormal noises from bottom end
• Verify oil pressure reaches normal specification within 5-10 seconds of startup (typically 40-60 PSI at idle when warm for this engine)
• Verify no oil leaks from oil pan, timing cover, or main bearing area after engine reaches operating temperature
• Verify no coolant leaks from cylinder heads or coolant system connections
• Test drive vehicle and verify smooth operation under load with no abnormal vibrations or noises
• Monitor oil pressure during test drive - pressure should remain stable and within specification under all conditions
• After test drive and cool-down, recheck oil level and top off if necessary (main bearing replacement may change oil retention slightly)
• After 500-1000 miles, perform oil and filter change to remove any break-in debris from new bearings

More procedures for this vehicle