Head Gaskets - Both

Complete removal and replacement of the cylinder head gasket on the 5.9L Cummins inline-6 diesel engine, including disassembly of valve train, timing components, and resurfacing preparation.

Warnings

Tools required

Parts

• Cylinder head gasket × 1 — Use OEM Cummins gasket
• Valve cover gasket × 1 — Use OEM specification
• Timing cover gasket × 1 — Use OEM specification
• Front crankshaft seal × 1 — Use OEM specification
• Exhaust manifold gasket × 1 — Use OEM specification
• Intake manifold gasket × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — M14 copper washer
• Cylinder head bolt set × 1 — Use OEM Cummins head bolts - often TTY
• Rocker arm assembly hardware × 1 — Inspect and replace as needed
• Coolant × 1 — HOAT type for later models, conventional green for early
• Engine oil × 1 — 15W-40 diesel rated
• Oil filter × 1 — Use OEM specification
• Fuel filter × 1 — Replace while accessible

Fluids

• 15W-40 diesel engine oil — 12 qt
• Ethylene glycol 50/50 (green conventional early, HOAT later) — 28 qt

Preparation

1. Park vehicle on level ground and engage parking brake. Chock rear wheels.
2. Disconnect both battery cables, negative first, then positive. Secure cables away from terminals.
3. Drain engine coolant by opening petcock on radiator and removing radiator cap when engine is completely cold.
4. Drain engine oil completely and remove oil filter. Inspect for metal contamination or coolant contamination.
5. Remove engine cover/doghouse from inside cab if equipped.
6. Remove both front wheels and inner fender wells for access to front timing cover.
7. Label and photograph all electrical connections, vacuum lines, and fuel lines before removal.
8. Relieve fuel system pressure per manufacturer procedure (typically by loosening fuel filter housing or using fuel pump relay removal method).
9. Support transmission with jack if removing engine mounts or accessories that affect engine position.
10. Clean engine exterior thoroughly to prevent contamination during internal work.

Procedure

1. 1

   Remove intake and exhaust systems
   Remove the air intake tube and air filter housing. Disconnect all boost tubes and intercooler piping. Remove the exhaust manifold by removing the turbocharger downpipe connection first, then the exhaust manifold nuts working from outside to center. Remove the intake manifold and intake grid heater assembly after disconnecting all electrical connections and fuel lines. Cap all open fuel ports immediately. Diesel fuel systems operate at very high pressure. On 1994-2002 models (mechanical P7100 or VP44 injection) and especially 2003-2007 common-rail models (up to ~23,000 PSI), relieve fuel pressure per the service procedure for your specific injection system before disconnecting any fuel lines to prevent injection injuries.
2. 2

   Remove valve cover and rocker assembly
   Remove valve cover bolts in reverse sequence (outside to center). Lift valve cover carefully as it may be sealed with RTV. Remove rocker arm assembly by loosening rocker arm bolts in sequence (always loosen when cam lobe is pointing away from rocker). Mark rocker arm positions if reusing. Remove pushrods and store in order - they must be reinstalled in original positions. Inspect pushrods for wear, bending, or damage.
   ⚠Pushrods must be reinstalled in their original positions. Use a numbered rack or label them 1-12 from front to rear.
   Torque spec

   Valve Cover Bolts10 Nm (7 lb-ft)
3. 3

   Remove front accessories and timing cover
   Remove serpentine belt and tensioner. Remove power steering pump and AC compressor, securing them aside without disconnecting hoses. Remove fan clutch and fan assembly. Remove crankshaft pulley using a puller (do not pry). Remove harmonic balancer bolt - this requires significant torque and may need an impact wrench. Mark balancer position before removal for reinstallation reference. Remove all timing cover bolts and carefully pry timing cover off, being careful not to damage sealing surfaces. The timing cover houses the front crankshaft seal which should be replaced. The crankshaft damper/pulley bolts are torqued to the factory Cummins specification (verify exact value in service manual). Use proper tools to avoid rounding fasteners.
   ⚠The harmonic balancer bolt is extremely tight (133 lb-ft). Use proper tools to avoid rounding the bolt head. Mark balancer position before removal for reinstallation reference.
   Torque spec

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

   Lock timing and remove camshaft drive
   Rotate engine to TDC on cylinder #1 (both valves closed, TDC pin engaged). On the 5.9L Cummins the camshaft is gear-driven with no timing chain, so cam gear removal is normally not required for a head gasket job. If access requires it, note the timing gear mark alignment on the cam gear and crankshaft gear, hold the camshaft with a wrench on the hex, then remove the cam gear retaining bolt and gear. Inspect timing gears for wear and backlash. The 5.9L Cummins uses a gear-driven timing system (crankshaft gear, cam gear, and injection pump gear), NOT a timing chain. There is no timing chain in this engine. Do not rotate crankshaft or camshaft independently once timing gears are separated. This can cause valve-to-piston contact and engine damage.
   ⚠️Do not rotate crankshaft or camshaft independently once timing chain is removed. This will cause valve-to-piston contact and engine damage.
   Torque spec

   Camshaft Sprocket Bolts80 Nm (59 lb-ft)
5. 5

   Remove cylinder head bolts
   Remove cylinder head bolts in reverse tightening sequence (outside to center, working in three passes). Start by loosening each bolt 1/4 turn in sequence, then 1/2 turn, then full removal. Keep bolts in order for inspection. Inspect all head bolts for necking, stretching, or thread damage. If bolts are torque-to-yield type (check service manual), they must be replaced and cannot be reused.
   ⚠Head bolts must be removed gradually in sequence to prevent warping the head. Never remove all bolts on one side first.
   Torque spec

   Cylinder Head Bolts88 Nm (65 lb-ft)
6. 6

   Remove cylinder head
   Install lifting hooks or chain to cylinder head lifting points. The 5.9L Cummins cylinder head is heavy (verify exact weight for your variant) and requires proper lifting equipment. Carefully break the head gasket seal using a plastic mallet or soft pry points. Never pry between machined sealing surfaces. Lift head straight up to avoid damaging dowel pins. Place head on clean, padded surface with fire deck facing up.
   ⚠️Never work under a suspended cylinder head. Use secure lifting equipment and have an assistant guide the head during removal.
7. 7

   Clean and inspect block deck surface
   Remove all old gasket material from block deck surface using a gasket scraper. Be extremely careful not to gouge or scratch the machined cast iron surface. Follow with solvent and lint-free rags. Use a straight edge and feeler gauge to check block deck for warpage at multiple points - maximum warpage is typically 0.002 inch. Check cylinder bore for scoring, excessive wear, or ridge at top. Inspect cylinder walls for cracks using dye penetrant if suspected damage.
   ⚠Any warpage beyond specification requires block resurfacing. Do not attempt to install head gasket on warped surfaces as it will fail immediately.
   Torque spec

   Gasket Surface Bolts20 Nm (15 lb-ft)
8. 8

   Inspect and service cylinder head
   Clean cylinder head fire deck thoroughly. Check head for cracks between valve seats and to water jackets using dye penetrant or magnetic particle inspection. Measure head surface flatness with straight edge and feeler gauge - maximum warpage typically 0.002 inch over length, 0.001 inch in any 6 inch span. If warped beyond spec, head must be resurfaced by machine shop. Inspect valves, seats, guides, and springs while head is off. Measure valve stem height after any machining to ensure proper geometry. Check camshaft bearings for scoring or excessive wear. Excessive milling of the head (more than 0.010 inch) will affect compression ratio and valve/piston clearance. Consult specifications for maximum material removal.
   ⚠Excessive milling of the head (more than 0.010 inch) will affect compression ratio, valve timing, and pushrod length. Consult specifications for maximum material removal.
9. 9

   Clean and prepare head bolt holes
   Clean all head bolt holes in the block thoroughly using a thread chaser and compressed air. Any oil, coolant, or debris in blind bolt holes can cause hydraulic lock and prevent proper bolt torque, or crack the block. Chase threads with proper tap to ensure clean threads. Some head bolts go into water jackets - apply appropriate sealant to these bolts per manufacturer specification. Inspect all bolt holes for damage or pulled threads.
   ⚠Failure to clean bolt holes can result in false torque readings and head gasket failure. Bolt holes must be completely dry and free of oil.
10. 10

    Install new head gasket and cylinder head
    Install new dowel pins if originals are damaged. Place new head gasket on block, ensuring correct orientation (typically marked 'TOP' or 'FRONT'). Do not use any sealant on the multi-layer steel head gasket unless specifically required by manufacturer. Carefully lower cylinder head onto block using lifting equipment, guiding it onto dowel pins. Ensure head seats fully on block before installing any bolts. Install new head bolts (if TTY type) finger tight in sequence.
    ⚠Head gasket must be installed in correct orientation. Reversed gaskets will block oil or coolant passages and cause immediate engine failure.
11. 11

    Torque cylinder head bolts
    Torque head bolts in the factory sequence using the multi-step procedure specified for your engine variant (12-valve vs 24-valve). Verify exact values against the Cummins/Dodge service manual for your year, as 12V and 24V specs differ. Typical 24-valve procedure: Step 1 to ~44 ft-lb, Step 2 to ~65 ft-lb, Step 3 to ~77 ft-lb in sequence, then final angle turn per manual. Confirm all values in the service manual before applying torque. 65 lb-ft plus 180 degrees total rotation. Allow 10-15 minutes for gasket to settle, then verify all bolts maintain angle.
    ⚠Head bolt sequence and torque procedure must be followed exactly. Improper torque or sequence will result in head gasket failure and possible head warpage.
    ⚠If any bolt fails to reach specification, stops turning, or turns too easily, stop immediately. The bolt or threads may be damaged.
    Torque spec

    Cylinder Head Bolts88 Nm (65 lb-ft)
12. 12

    Reinstall timing components
    Ensure crankshaft is still at TDC for cylinder #1. If the cam gear was removed, align the cam gear timing mark to the crankshaft gear mark per factory specification. Install the gear on the camshaft while holding the cam with a wrench on the hex, then install and torque the cam gear retaining bolt. Verify gear timing marks and backlash are correct. Rotate engine two complete revolutions by hand and verify timing marks realign and no valve contact occurs.
    ⚠️Incorrect timing will cause catastrophic valve-to-piston contact when engine is started. Verify timing marks multiple times before proceeding.
    Torque spec

    Camshaft Sprocket Bolts80 Nm (59 lb-ft)

    Timing Chain Tensioner Bolt25 Nm (18 lb-ft)
13. 13

    Install timing cover and front accessories
    Install new front crankshaft seal in timing cover using seal driver. Clean timing cover mating surface and apply new gasket or RTV per manufacturer specification. Install timing cover and torque bolts in sequence. Install harmonic balancer with keyway aligned to crankshaft key. Torque crankshaft pulley bolt to specification. Reinstall water pump if removed. Reinstall power steering pump, AC compressor, fan assembly, and serpentine belt. Ensure all accessories are properly aligned and tensioned.
    ⚠Harmonic balancer must be installed with timing marks aligned. Some balancers require new bolt or thread locker application.
    Torque spec

    Timing Cover Bolts - 8mm25 Nm (18 lb-ft)

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)
14. 14

    Install pushrods and rocker assembly
    Install pushrods in their original positions, ensuring they seat properly in lifter cups (rotate pushrod while pressing down to verify seating). Apply assembly lube to rocker arm contact points. Install rocker arm assembly and finger tighten bolts. Rotate crankshaft to position each cylinder at base circle (cam lobe pointing away from rocker) before torquing that cylinder's rocker bolts. Torque rocker arm bolts to specification in two steps. Perform valve lash adjustment - this is required on the 5.9L Cummins, which uses solid lifters with adjustable rockers. Set intake and exhaust valve lash to factory specification (typically 0.010 in intake, 0.020 in exhaust for 24V; verify for your variant) with the cylinder at TDC compression.
    ⚠Rocker bolts must only be torqued when cam lobe is pointing away from the rocker. Torquing on cam peak will damage valvetrain components.
    Torque spec

    Rocker Arm Bolts30 Nm (22 lb-ft)
15. 15

    Reinstall valve cover and remaining components
    Clean valve cover and mating surface thoroughly. Install new valve cover gasket (use RTV in corners if specified). Install valve cover and torque bolts in sequence from center outward. Reinstall intake manifold with new gasket and torque bolts to specification. Reinstall exhaust manifold with new gasket and torque nuts to specification from center outward. Reinstall turbocharger connections and all boost piping. Reconnect all fuel lines, electrical connections, and vacuum lines per labels and photos. Install new oil filter and close oil drain plug with new crush washer. Refill cooling system with proper coolant mixture. Refill engine with proper diesel engine oil (12 quarts). Reinstall inner fender wells and wheels. Reconnect battery cables (positive first, then negative).
    ⚠Verify all electrical connections are properly secured before starting engine. Loose connections can cause sensor faults or no-start conditions.
    Torque spec

    Valve Cover Bolts10 Nm (7 lb-ft)

    Intake Manifold Bolt24 Nm (18 lb-ft)

    Exhaust Manifold Nuts34 Nm (25 lb-ft)

    Oil Drain Plug35 Nm (26 lb-ft)

Reassembly

1. Torque specifications must be followed exactly - this is critical for head gasket sealing and engine longevity
2. All gaskets and seals should be replaced - reusing old gaskets will result in leaks
3. Pushrods must be reinstalled in original positions to maintain proper valve train geometry
4. Head bolts are typically torque-to-yield and must be replaced with new bolts
5. Timing marks must be verified multiple times before and after installation
6. All bolt hole threads should be cleaned and chased before installation

Verification

• Before starting: Rotate engine by hand two complete revolutions to verify no binding or valve contact. Should rotate smoothly with normal compression resistance.
• Check that all electrical connections are secure and all vacuum lines are connected.
• Verify coolant level is correct and system is properly bled of air pockets (run until thermostat opens, add coolant as needed).
• Check engine oil level on dipstick - should be at full mark after filling with 12 quarts.
• Start engine and monitor for unusual noises, especially valve train clicking or knocking. Some lifter noise is normal for first few seconds.
• Check for coolant leaks, oil leaks, and fuel leaks while engine warms up. Pay special attention to head gasket sealing areas.
• Monitor engine temperature - should reach normal operating temperature and thermostat should open normally.
• Check for exhaust leaks at manifold gasket and turbo connections.
• After engine reaches operating temperature and is shut off, allow to cool and recheck head bolt torque (if specified by manufacturer - some require retorque after initial heat cycle).
• Road test vehicle under light load initially, then gradually increase load. Monitor for overheating, loss of power, or excessive smoke.
• Recheck all fluid levels after initial run period. Check for leaks again after first 50-100 miles.
• Change engine oil and filter after first 500 miles to remove any assembly debris or break-in contaminants.

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