This procedure covers removal, machining, and reinstallation of the cylinder heads on a 2012-2018 Jeep Wrangler 3.6L V6 engine, including valve train disassembly and head gasket replacement.

Warnings

Tools required

Parts

• Cylinder head gasket set × 1 — Use OEM specification
• Valve cover gaskets × 2 — Use OEM specification
• Intake manifold gaskets × 1 — Use OEM specification
• Exhaust manifold gaskets × 2 — Use OEM specification
• Cylinder head bolts (TTY) × 1 — Use OEM specification
• Spark plugs × 6 — Use OEM specification
• Engine oil filter × 1 — Use OEM specification

Fluids

• Mopar OAT Coolant (Purple) — 13 qt
• Mopar 5W-20 Synthetic Blend — 6.5 qt

Preparation

1. Ensure engine is completely cool before beginning work
2. Disconnect negative battery cable and isolate terminal
3. Remove engine cover by pulling upward on cover
4. Drain coolant completely from radiator and engine block drain plugs into suitable container
5. Drain engine oil and remove oil filter
6. Relieve fuel system pressure by removing fuel pump fuse and running engine until it stalls
7. Remove air intake system and air filter housing
8. Label and photograph all vacuum lines, electrical connectors, and hose routing for reassembly reference

Procedure

1. 1

   Remove valve covers and accessory components
   Disconnect ignition coil connectors and remove all six ignition coils. Remove PCV hoses and breather hoses from valve covers. Remove valve cover bolts in a crisscross pattern and carefully lift off both valve covers. Remove the upper intake manifold plenum and throttle body assembly. Disconnect all fuel lines using proper fuel line disconnect tools.
   ⚠Fuel system is under pressure. Have shop towels ready to catch residual fuel when disconnecting fuel lines.
   Torque spec

   Cover Bolts19 Nm (14 lb-ft)
2. 2

   Remove intake and exhaust manifolds
   Disconnect all electrical connectors from intake manifold including MAP sensor and fuel injectors. Remove lower intake manifold bolts and carefully lift manifold assembly off engine. Remove exhaust manifold heat shields. Remove exhaust manifold bolts from both left and right manifolds working from center outward. Separate exhaust manifolds from cylinder heads.
   Torque spec

   Mounting Bolts54 Nm (40 lb-ft)

   Sensor Bolts12 Nm (9 lb-ft)
3. 3

   Set engine to TDC and mark timing components
   Rotate crankshaft clockwise until cylinder #1 is at top dead center on compression stroke. Verify timing marks on camshaft sprockets align with marks on timing chain cover. Use paint marker to mark timing chain position relative to all camshaft sprockets and crankshaft sprocket. Take clear photos of timing chain routing and tensioner positions.
   ⚠Accurate timing mark documentation is critical. Incorrect reassembly will cause engine damage.
4. 4

   Remove timing chain and camshaft components
   Install engine support fixture to support engine weight. Remove engine mount bolts as necessary to lower engine for timing cover access. Remove timing chain cover bolts and carefully pry cover away from engine block. Release timing chain tensioners by rotating tensioner pawl. Remove timing chain guide bolts. Use camshaft holding tool to prevent camshaft rotation and remove camshaft sprocket bolts. Remove timing chain from sprockets. Mark and remove all four camshaft bearing caps in reverse order of tightening sequence (outside to inside). Carefully lift camshafts from cylinder heads keeping them in order for reinstallation.
   Torque spec

   Mounting Bolts54 Nm (40 lb-ft)
5. 5

   Remove rocker arms and valve components
   Remove rocker arm assemblies from both cylinder heads, keeping each rocker arm with its respective valve position. Use valve spring compressor to compress valve springs and remove valve locks, retainers, and springs if valve service is required. Store all components in organized manner labeled by cylinder number and position. Inspect all valve train components for wear or damage.
   ⚠Valve springs are under significant tension. Ensure valve spring compressor is properly seated before removing valve locks.
6. 6

   Remove cylinder head bolts and heads
   Remove cylinder head bolts in reverse order of tightening sequence, starting from outer bolts working inward in a crisscross pattern. Loosen each bolt 1/4 turn at a time to prevent head warping. Once all bolts are removed, carefully lift cylinder head straight up from engine block using lifting points. If head is stuck, gently tap with rubber mallet at corners near gasket surface. Never pry between head and block surfaces. Place cylinder heads on clean padded surface with combustion chambers facing up.
   Torque spec

   Gasket Surface Bolts23 Nm (17 lb-ft)
7. 7

   Inspect and prepare heads for machining
   Remove all carbon deposits from combustion chambers using appropriate cleaning methods. Inspect cylinder head for cracks, especially between valve seats and in exhaust ports. Check head flatness using precision straightedge and feeler gauge across multiple planes. Document any warpage measurements. Cylinder heads requiring more than 0.004 inches removal should be evaluated for suitability. Transport heads to qualified machine shop for resurfacing, pressure testing, and valve seat inspection. Provide machinist with manufacturer specifications for surface finish (30-60 RA) and maximum material removal limits.
   ℹ️Machine shop should verify valve stem height after resurfacing. Excessive resurfacing may require valve seat machining or component replacement.
8. 8

   Clean and inspect engine block surfaces
   Clean cylinder head mating surfaces on engine block thoroughly using plastic razor blade scraper. Remove all old gasket material without scratching or gouging aluminum surfaces. Clean bolt holes using appropriate tap or thread chaser to remove debris and old thread sealant. Inspect block deck surface for flatness and damage. Cover open cylinders with clean shop towels to prevent debris entry. Clean all oil passages and coolant passages in block. Inspect cylinder bores for scoring or damage while heads are removed.
   Torque spec

   Gasket Surface Bolts23 Nm (17 lb-ft)
9. 9

   Install resurfaced cylinder heads
   Verify resurfaced heads are clean and dry. Install new head locating dowels if removed. Place new head gaskets on block ensuring proper orientation (TOP marking faces up). Carefully lower cylinder heads onto block, aligning with dowel pins. Install new TTY cylinder head bolts (do not reuse old bolts) finger tight. Following manufacturer tightening sequence, torque head bolts in four stages: Stage 1 - torque all bolts to 25 ft-lb, Stage 2 - torque all bolts to 40 ft-lb, Stage 3 - rotate all bolts 90 degrees, Stage 4 - rotate all bolts an additional 90 degrees. Verify each bolt has been properly torqued using sequence chart.
   ⚠️Head bolt tightening sequence and torque-to-yield procedure must be followed exactly. Improper installation will cause head gasket failure.
   Torque spec

   Gasket Surface Bolts23 Nm (17 lb-ft)
10. 10

    Reinstall valve train components
    If valves were removed, reassemble valve springs, retainers, and locks using valve spring compressor. Lubricate all valve stems with clean engine oil. Install rocker arms in their exact original positions. Apply assembly lubricant to camshaft journals and lobes. Carefully install camshafts in their original positions (intake and exhaust marked). Install camshaft bearing caps in correct order and orientation following tightening sequence from center caps outward. Torque camshaft cap bolts to specification incrementally.
    Torque spec

    Mounting Bolts54 Nm (40 lb-ft)
11. 11

    Install timing chain and components
    Verify crankshaft is still at TDC position. Install timing chain onto crankshaft sprocket first, then route chain over camshaft sprockets aligning with reference marks made during disassembly. Install camshaft sprocket bolts using camshaft holding tool and torque to specification. Install timing chain guides and tensioners. Verify all timing marks align correctly before proceeding. Clean timing cover gasket surfaces and install new gasket. Apply small amount of RTV sealant at engine block to oil pan junction points. Install timing cover and torque bolts to specification. Reinstall engine mounts.
    Torque spec

    Mounting Bolts54 Nm (40 lb-ft)

    Gasket Bolts23 Nm (17 lb-ft)
12. 12

    Install manifolds and remaining components
    Install new exhaust manifold gaskets and mount exhaust manifolds to cylinder heads. Torque exhaust manifold bolts from center outward. Install new intake manifold gaskets ensuring proper sealing at all ports. Install lower intake manifold and torque bolts in proper sequence from center outward. Reconnect fuel injector connectors and all intake manifold sensors. Install upper intake plenum with new gasket. Reconnect throttle body and all vacuum lines per reference photos.
    Torque spec

    Gasket Bolts23 Nm (17 lb-ft)

    Mounting Bolts54 Nm (40 lb-ft)
13. 13

    Install valve covers and ignition system
    Clean valve cover mating surfaces thoroughly. Install new valve cover gaskets ensuring proper seating in gasket channels. Apply small dab of RTV sealant at camshaft cap corners where indicated by service manual. Install valve covers and torque bolts in crisscross pattern. Reconnect PCV and breather hoses. Install new spark plugs gapped to specification. Install ignition coils and torque bolts. Reconnect all ignition coil electrical connectors.
    Torque spec

    Cover Bolts19 Nm (14 lb-ft)

    Electrical Connector Bolts8 Nm (6 lb-ft)
14. 14

    Refill fluids and final preparation
    Install new oil filter and refill engine with 6.5 quarts of Mopar 5W-20 synthetic blend oil. Close coolant drain plugs and refill cooling system with 13 quarts of Mopar OAT purple coolant using proper bleeding procedure. Reconnect negative battery cable. Reinstall air intake system and engine cover. Double-check all electrical connections, hoses, and bolts for proper installation.

Reassembly

1. Ensure all torque specifications have been met using proper torque wrenches
2. Verify timing chain alignment marks are correctly positioned before starting engine
3. Check that all electrical connectors are fully seated and locked
4. Confirm all fluid levels are correct and no leaks are present at gasket surfaces

Verification

• Start engine and verify it runs smoothly without unusual noises or vibrations
• Monitor for coolant, oil, or fuel leaks around cylinder heads, valve covers, intake and exhaust manifolds
• Allow engine to reach operating temperature and verify cooling fans cycle properly
• Check for proper oil pressure on instrument cluster
• Bleed cooling system completely by running engine with heater on high until thermostat opens and air is purged
• After initial warm-up and cool-down cycle, recheck all fluid levels and inspect for any seepage
• Perform test drive and verify normal engine operation under load with no misfires or performance issues
• Scan for diagnostic trouble codes to ensure no sensor or timing-related codes are present

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