Valve Seals

Replace valve stem seals on the VQ35DE V6 engine to address oil consumption or smoke on startup, requiring removal of camshafts and valve train components.

Warnings

Tools required

Parts

• Valve stem seal set (24 seals for VQ35DE) × 1 — Use OEM Nissan specification
• Valve cover gaskets (left and right) × 2 — Use OEM specification
• Valve cover grommet/seal set × 1 — Use OEM specification
• Timing chain cover gasket × 1 — Use OEM specification
• Camshaft position sensor O-rings × 4 — Use OEM specification
• RTV silicone sealant (Nissan specified or equivalent) × 1 — Use OEM specification
• Engine oil × 1 — 5W-30 synthetic blend

Fluids

• 5W-30 synthetic blend engine oil — 4.88 qt
• Nissan Blue Long Life Coolant (pre-diluted) — 1.5 qt

Preparation

1. Ensure engine is completely cold to touch
2. Disconnect negative battery cable and wait 3 minutes for airbag system discharge
3. Remove engine cover (decorative plastic cover on top of engine)
4. Relieve fuel system pressure by removing fuel pump fuse and cranking engine until it dies
5. Drain coolant into appropriate container by opening radiator drain and removing upper radiator hose at thermostat housing
6. Remove air intake assembly from throttle body to air filter box
7. Label and photograph all vacuum lines, electrical connections, and hose routing before removal
8. Support engine with fixture or jack under oil pan (with wood block protection) as motor mount will be removed

Procedure

1. 1

   Remove valve covers and upper engine accessories
   Remove ignition coils (one bolt each, disconnect harness). Remove all 10 valve cover bolts from each side. Lift off both valve covers carefully. Remove PCV hoses and breather tubes. Disconnect variable valve timing solenoid connectors on front of each cylinder head. Remove intake manifold plenum if access is restricted (6 bolts securing upper plenum to lower manifold).
2. 2

   Remove right side motor mount and timing chain cover
   Remove right side engine mount assembly (3 bolts to engine bracket, 2 through-bolts to frame). Support engine weight with fixture. Remove crankshaft pulley bolt (high torque, 22mm socket, use breaker bar, engine must be prevented from rotating). Remove crankshaft pulley. Remove timing chain front cover (14 bolts around perimeter). Carefully pry cover away from block, breaking RTV seal. Note the location of two different length bolts during removal.
3. 3

   Mark timing chain alignment and verify TDC position
   Rotate crankshaft to position number 1 cylinder at TDC compression stroke (both camshaft lobes for cylinder 1 pointing away from valves, timing marks on camshaft sprockets aligned with timing marks on chain). Use paint pen or permanent marker to mark timing chain position on both camshaft sprockets and on crankshaft sprocket. Take multiple reference photos. Verify TDC by inserting long screwdriver into spark plug hole and confirming piston is at top dead center. Mark crankshaft position relative to block with paint pen.
4. 4

   Remove camshaft sprocket bolts and secure timing chain
   Hold each camshaft with holding tool or large adjustable wrench on camshaft hex section. Remove camshaft sprocket bolts from both intake and exhaust camshafts on each bank (4 bolts total, located at center of sprockets). Do NOT allow camshaft sprockets to rotate. Use wire or zip ties to secure timing chain to prevent it from falling into timing chain cavity. Carefully slide sprockets off camshafts while keeping chain supported and in position.
   ⚠If timing chain falls into lower chain cavity, front engine case must be removed to retrieve it. Keep constant tension and support on chain.
5. 5

   Remove camshaft bearing caps and camshafts
   Loosen all camshaft bearing cap bolts in reverse order from outside to inside in multiple passes (2-3 turns each pass) to gradually release valve spring pressure. There are 10 bearing caps per camshaft (4 camshafts total). Each cap is numbered and marked with intake/exhaust designation - note orientation. Remove bolts completely and lift off bearing caps. Carefully lift out all four camshafts and place on clean padded surface. Keep camshafts in order (right bank intake, right bank exhaust, left bank intake, left bank exhaust).
   ⚠Camshaft bearing caps must be reinstalled in exact same positions and orientations. Swapping positions will cause bearing failure.
6. 6

   Remove rocker arms and lash adjusters
   Remove all 24 rocker arms (12 per cylinder head) and place in organized tray maintaining position order. Remove all 24 hydraulic lash adjusters from their bores in cylinder heads. Keep lash adjusters upright (do not lay on side) to prevent oil from draining out. Label or organize all components to ensure reinstallation in original positions.
   ℹ️Rocker arms and lash adjusters must return to their original positions. Create a labeled diagram or use compartmented tray.
7. 7

   Set up for valve seal replacement on cylinder 1
   Remove spark plug from cylinder 1. Rotate crankshaft to bring cylinder 1 piston approximately 1 inch before top dead center (to prevent valve from hitting piston during spring compression). Thread air hose adapter into spark plug hole. Connect compressed air supply and pressurize cylinder to 90-100 psi. Verify piston is held in position by attempting gentle rotation of crankshaft - it should not move. Maintain air pressure throughout seal replacement on this cylinder.
   ⚠️Never remove air pressure while valve spring is compressed or valve will drop into cylinder. Always release spring compressor before removing air.
8. 8

   Compress valve springs and remove keepers for cylinder 1
   Using overhead cam valve spring compressor, compress intake valve spring for cylinder 1 until valve keepers (collets) are accessible. Use magnetic pick-up tool to carefully remove both valve keepers and place in labeled container. Slowly release spring compressor and remove. Remove valve spring retainer and valve spring. Note spring orientation. Repeat process for exhaust valve on cylinder 1. Keep all components organized by cylinder and valve position.
   ⚠Valve keepers are small and easily lost. Work over clean mat or container. If keeper falls into engine, it must be retrieved before proceeding.
9. 9

   Remove old valve seals and clean valve stem for cylinder 1
   Using valve seal removal tool or needle nose pliers, carefully grip old valve seal at base and pull straight up off valve guide. Seal will be tight - rock gently side to side while pulling. Inspect valve stem for any scoring or damage. Clean valve stem and valve guide top thoroughly with brake cleaner and lint-free cloth. Verify valve moves freely in guide (air pressure should hold valve up against seat). Repeat for exhaust valve on cylinder 1.
   ℹ️If valve stem shows scoring or if valve does not seal properly under air pressure, valve guide wear is excessive and further cylinder head service is required.
10. 10

    Install new valve seals for cylinder 1
    Lightly oil new valve seal inner diameter with clean engine oil. Place new seal on valve seal installation tool (correct tool has plastic sleeve to protect seal from valve keeper groove during installation). Slide seal down over valve stem carefully. Using installation tool, press seal down onto valve guide until it bottoms out with firm resistance. Seal should be fully seated on guide with uniform appearance. Do not strike seal directly with hammer. Repeat process for exhaust valve. Verify seals are fully seated and centered on guides.
    ⚠Valve seal must pass over sharp keeper groove on valve stem without tearing. Use proper installation tool with protective sleeve.
11. 11

    Reinstall springs, retainers, and keepers for cylinder 1
    Install valve spring over valve stem (confirm correct orientation if spring has tighter wound coils on one end - tighter coils go toward cylinder head). Install valve spring retainer. Using valve spring compressor, compress spring until retainer is below keeper groove. Apply small amount of grease to valve keepers to hold them in position. Carefully install both keepers into groove using magnetic tool or small screwdriver. Slowly release spring compressor while ensuring keepers remain seated. Tap top of valve stem gently with plastic tool to verify keepers are locked in place. Repeat for exhaust valve on cylinder 1.
    ⚠Verify keepers are fully seated before releasing spring compressor. Improperly seated keepers will release under spring pressure causing valve to drop.
12. 12

    Complete valve seal replacement for remaining cylinders
    Release air pressure from cylinder 1. Remove air adapter and install spark plug finger tight. Move to cylinder 2 by rotating crankshaft to bring cylinder 2 to approximately 1 inch before TDC compression stroke (reference firing order: 1-2-3-4-5-6 corresponds to specific cylinder positions). Install air adapter and pressurize cylinder 2. Repeat steps 8 through 11 for both valves on cylinder 2. Continue this process for all six cylinders (cylinders 3, 4, 5, and 6), completing both intake and exhaust valve seals on each cylinder before moving to next cylinder. Total of 24 valve seals will be replaced.
    ℹ️Maintain careful organization throughout this process. Each cylinder requires 20-30 minutes for both valves. Plan for breaks to maintain concentration and quality.
13. 13

    Reinstall hydraulic lash adjusters and rocker arms
    Ensure each hydraulic lash adjuster is returned to its original bore position. Install all 24 lash adjusters into cylinder heads - they should slide in with light resistance. Install rocker arms over lash adjusters and valve stem tips in their original positions. Verify each rocker arm sits properly on both lash adjuster and valve stem tip with rocker pad centered on valve tip.
14. 14

    Reinstall camshafts and bearing caps
    Apply light coat of clean engine oil to all camshaft journals and lobes. Carefully lower each camshaft into its original position in cylinder head (ensure intake and exhaust camshafts are in correct positions - verify by camshaft identification marks). Position camshafts with lobes for cylinder 1 pointing away from valves (TDC position). Apply light engine oil to bearing cap journals. Install all bearing caps in their exact original positions with numbered and intake/exhaust marks facing toward front of engine. Install bearing cap bolts finger tight. Torque bearing cap bolts in sequence from center caps outward in three progressive steps: first pass to 7 Nm, second pass to 15 Nm, final pass to 23 Nm. Verify camshafts rotate freely by hand after torque is applied.
    ⚠Bearing cap bolt torque sequence is critical. Improper sequence or torque will damage camshaft journals or bearing caps.
    Torque spec

    Mounting Bolts55 Nm (40 lb-ft)
15. 15

    Reinstall camshaft sprockets and verify timing alignment
    Position timing chain onto crankshaft sprocket. Verify crankshaft is still at TDC position marked earlier. Lift timing chain and install camshaft sprockets onto camshafts while aligning timing marks on chain with marks on sprockets (reference marks made in step 3). Install camshaft sprocket bolts finger tight. Hold each camshaft with holding tool and torque sprocket bolts to 55 Nm. Rotate engine by hand two complete revolutions and verify all timing marks realign perfectly at TDC. If marks do not align, timing chain installation is incorrect and must be corrected before proceeding.
    ⚠️Incorrect valve timing will cause immediate engine damage on startup. Triple-check all timing marks before proceeding.
    Torque spec

    Mounting Bolts55 Nm (40 lb-ft)
16. 16

    Install timing chain cover with new gasket
    Clean all RTV sealant residue from timing chain cover mating surface and engine block mating surface using plastic scraper and brake cleaner. Apply new gasket to timing cover or apply continuous 3mm bead of RTV sealant to cover mating surface (follow Nissan service manual specification for RTV or gasket use). Install timing cover onto engine, guiding over crankshaft snout. Install all 14 cover bolts and torque in star pattern to 19 Nm. Allow RTV to cure for 30 minutes before adding fluids if RTV was used.
    Torque spec

    Cover Bolts19 Nm (14 lb-ft)
17. 17

    Reinstall crankshaft pulley and right motor mount
    Install crankshaft pulley onto crankshaft snout (ensure pulley key is aligned with keyway). Install crankshaft pulley bolt and torque to specification (verify exact specification for 2012 Altima VQ35DE - typically 98-118 Nm plus angle torque). Install right side engine mount assembly and torque mounting bolts to 55 Nm for engine bracket bolts and 31 Nm for through-bolts to frame. Remove engine support fixture.
    Torque spec

    Mounting Bolts55 Nm (40 lb-ft)
18. 18

    Install valve covers with new gaskets
    Clean valve cover mating surfaces on cylinder heads thoroughly. Install new valve cover gaskets into valve cover grooves (gaskets should snap into place). Apply small dab of RTV at front corners where timing chain cover meets cylinder head. Position valve covers onto cylinder heads and install bolts. Torque valve cover bolts in sequence from center outward to 23 Nm. Reinstall PCV hoses, breather tubes, and variable valve timing solenoid connectors.
    Torque spec

    Gasket Bolts23 Nm (17 lb-ft)
19. 19

    Reinstall remaining components and refill fluids
    Reinstall intake manifold plenum if removed, torque bolts to 23 Nm. Install new spark plugs (if not already done) gapped to 1.1mm and torque to 25 Nm. Install ignition coils and torque bolts to 12 Nm. Reinstall air intake assembly. Refill cooling system with 1.5 quarts of Nissan Blue Long Life Coolant (pre-diluted) - only replacing amount drained during procedure. Reconnect negative battery cable.
    Torque spec

    Gasket Bolts23 Nm (17 lb-ft)

    Sensor Bolts12 Nm (9 lb-ft)
20. 20

    Perform initial startup and valve train break-in
    Verify oil level is at full mark. Start engine and allow to idle. Listen carefully for any unusual valve train noise - slight ticking for first 30-60 seconds is normal as lash adjusters pump up. Monitor for oil leaks at valve covers and timing cover. Allow engine to reach operating temperature (coolant temperature gauge at normal position). Check for proper idle quality and smooth operation. Perform several gentle acceleration cycles to varying RPM ranges. Shut off engine and recheck oil level after 5 minute settling period.
    ⚠If loud valve train noise persists beyond 60 seconds or if any metallic knocking is heard, shut down immediately and investigate. Noise may indicate valve keeper failure or timing issue.

Reassembly

1. All valve train components must be returned to original positions - never swap rocker arms or lash adjusters between positions
2. Camshaft bearing caps are position-specific and directional - verify marks before installation
3. Torque all fasteners to specification in proper sequence - critical for sealing and component life
4. Timing chain alignment must be verified by rotating engine two full revolutions and confirming marks realign
5. New valve cover gaskets and timing cover gasket are required - do not reuse old gaskets

Verification

• Start engine and verify smooth idle with no excessive valve train noise after initial 60 second pump-up period
• Check for oil leaks at valve covers, timing chain cover, and all gasket surfaces
• Verify no coolant leaks after engine reaches operating temperature
• Monitor oil consumption over next 500 miles - should be dramatically reduced if valve seals were the issue
• Check for blue smoke on cold startup (first start of day) - should be eliminated or greatly reduced
• Verify proper engine performance with no hesitation, rough idle, or loss of power
• Recheck valve cover bolt torque after first heat cycle (after engine cools)
• Monitor oil level closely for first few drive cycles to ensure seals are functioning properly