Long Block Replacement

Complete removal and replacement of the 5.9L Cummins diesel long block assembly, including transfer of external components from the old engine to the new long block.

Warnings

Tools required

Parts

• 5.9L Cummins long block assembly × 1 — Use OEM specification
• Engine oil filter × 1 — Use OEM specification
• Fuel filter/water separator × 1 — Use OEM specification
• Engine coolant thermostat × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Oil cooler gaskets × 1 — Use OEM specification
• Exhaust manifold gaskets × 1 — Use OEM specification
• Turbocharger mounting gasket × 1 — Use OEM specification
• Intake manifold gasket × 1 — Use OEM specification
• Front crankshaft seal × 1 — Use OEM specification
• Rear main seal × 1 — Use OEM specification
• Valve cover gasket × 1 — Use OEM specification
• Engine mount bolts × 1 — Use OEM specification
• Serpentine belt × 1 — Use OEM specification

Fluids

• 15W-40 diesel oil or 5W-40 synthetic — 12 qt
• HOAT coolant 50/50 — 28 qt
• R-134a refrigerant

Preparation

1. Park vehicle on level surface and engage parking brake. Place wheel chocks behind rear wheels
2. Disconnect both battery cables (negative first, then positive) and remove batteries
3. Drain engine oil completely and remove oil filter
4. Drain cooling system from radiator petcock and block drain plugs
5. Recover AC refrigerant using certified AC recovery machine
6. Remove engine cover/doghouse from inside cab
7. Remove hood for better access (mark hinge positions for reinstallation)
8. Relieve fuel system pressure by loosening fuel filter bleed screw
9. Label all electrical connectors, vacuum lines, and hoses with tape and marker before disconnection

Procedure

1. 1

   Remove radiator and cooling system components
   Disconnect upper and lower radiator hoses from engine. Remove radiator shroud bolts and lift shroud up and over fan. Disconnect transmission cooler lines from radiator. Remove radiator mounting bolts and lift radiator out of vehicle. Disconnect heater hoses from engine. Remove intercooler inlet and outlet tubes.
2. 2

   Disconnect AC and power steering systems
   Disconnect AC compressor lines at firewall (refrigerant already recovered). Cap all open AC fittings immediately. Remove power steering pump mounting bolts and set pump aside with hoses attached (do not disconnect hoses). Support power steering pump to prevent hose damage.
3. 3

   Remove air intake system and turbocharger connections
   Remove air intake tube from turbocharger inlet. Disconnect all intake grid heater wiring. Disconnect exhaust downpipe from turbocharger outlet (V-band clamp or bolted flange, depending on configuration). Note fastener count and orientation before removal. Support exhaust system to prevent damage.
4. 4

   Disconnect fuel system
   Disconnect fuel supply and return lines at fuel filter housing using proper fuel line disconnect tools. Cap all open fuel lines to prevent contamination. Disconnect fuel heater electrical connector. Remove fuel filter assembly if it will interfere with engine removal. Disconnect accelerator linkage and cruise control cable if equipped.
5. 5

   Disconnect electrical connections
   Disconnect engine wiring harness at firewall connector (main engine harness connector). Disconnect alternator wiring. Disconnect starter motor cables and wiring. Disconnect all sensors including coolant temperature sensor, oil pressure sensor, crankshaft position sensor, intake air temperature/pressure sensor, and camshaft/engine speed sensor if equipped. Disconnect intake air grid heater relay and grid heater connections (note: Cummins uses a grid heater, not glow plugs).
6. 6

   Remove serpentine belt and accessories
   Release belt tensioner and remove serpentine drive belt. Remove alternator mounting bolts and remove alternator. Remove AC compressor mounting bolts and secure compressor out of the way without disconnecting refrigerant lines. Remove fan and fan clutch assembly (requires special fan clutch wrench; note the Cummins fan clutch nut is typically LEFT-HAND thread — verify before applying force). Remove fan shroud completely if not already removed.
7. 7

   Separate transmission from engine
   Place transmission jack under transmission and secure transmission. Remove transmission bellhousing-to-engine block bolts (verify exact count and locations for the specific transmission — 48RE automatic or G56 manual — before removal). For manual transmission, disconnect clutch hydraulic line. For automatic transmission, note torque converter orientation and remove torque converter-to-flexplate bolts through starter opening. Carefully slide transmission back approximately 2 inches to disengage input shaft from clutch or torque converter from crankshaft. Support transmission securely on transmission jack.
8. 8

   Disconnect exhaust manifold and remaining engine mounts
   If not already removed, disconnect exhaust manifold from cylinder head (will be transferred to new long block). Remove engine mount through-bolts on both driver and passenger sides. Check that all connections to engine are disconnected - fuel, electrical, coolant, vacuum, AC, power steering.
9. 9

   Attach engine hoist and remove engine
   Attach engine hoist chains or straps to the factory engine lift brackets/eyes using proper lifting points rated for the ~1,100+ lb engine weight. Install engine leveler on hoist hook. Carefully raise engine slightly to take tension on chains and verify balance. Slowly lift engine while tilting front slightly upward to clear transmission input shaft or torque converter. Guide engine forward and up, watching for any missed connections. Once clear of engine bay, lower engine onto sturdy engine stand or heavy-duty work surface.
10. 10

    Transfer external components from old engine to new long block - front components
    Transfer the following components from old engine to new long block: front engine cover with crankshaft pulley and harmonic balancer, oil pump (if external or front-mounted), water pump, thermostat housing with thermostat, oil cooler and lines, fuel pump (if engine-mounted), injection pump (transfer carefully, noting timing marks and position), fuel injector lines and injectors (keep in order by cylinder), glow plugs or intake grid heater.
11. 11

    Transfer external components - rear and top components
    Transfer the following components: flywheel or flexplate (mark position relative to crankshaft before removal), rear engine cover/housing, valve cover with breather system, intake manifold with all sensors and connections, exhaust manifolds, turbocharger assembly with all oil feed and drain lines, engine lift brackets, dipstick tube, oil filter housing/adapter, all sensors (coolant temp, oil pressure, cam sensor, crank sensor), engine wiring harness brackets and ground straps.
12. 12

    Install new long block into vehicle
    Attach engine hoist to new long block assembly using lifting brackets. Carefully lift engine and position over engine bay. Tilt front of engine slightly upward and guide engine into position, aligning with transmission. Guide engine rearward onto transmission, ensuring transmission input shaft enters clutch disc pilot bearing (manual) or torque converter hub enters crankshaft properly (automatic). Lower engine onto engine mounts, aligning mount holes.
13. 13

    Install engine mounts and reconnect transmission
    Install engine mount through-bolts on both sides and tighten to FSM-specified torque value. Install all transmission bellhousing-to-engine block bolts and tighten to FSM-specified torque in a crossing pattern. For automatic transmission, install torque converter-to-flexplate bolts through starter opening, ensuring torque converter is fully seated in transmission pump. Remove transmission jack once transmission is secured to engine. Remove engine hoist once engine is stable.
14. 14

    Reconnect accessories and engine systems
    Install AC compressor with new mounting bolts. Install alternator with mounting bolts. Install power steering pump. Install serpentine belt on all pulleys and verify proper routing. Reconnect all electrical connectors to sensors, alternator, starter, and main engine harness at firewall. Reconnect fuel supply and return lines using new O-rings if applicable. Reconnect accelerator linkage and cruise control cable.
15. 15

    Install cooling system and final connections
    Install radiator into vehicle with mounting bolts. Reconnect transmission cooler lines to radiator. Install radiator shroud. Reconnect upper and lower radiator hoses with new clamps. Reconnect heater hoses. Install intercooler tubes. Reconnect AC lines at firewall with new O-rings. Install exhaust downpipe to turbocharger outlet with new gasket. Fill cooling system with proper HOAT (G-05 spec) 50/50 coolant mixture (verify total system capacity per FSM, approximately 5-6 gallons). Install new oil filter, then fill engine with proper diesel-rated oil (15W-40 or 5W-40 synthetic) — approximately 12 quarts with filter; verify exact capacity per FSM.

Reassembly

1. Reinstall engine cover/doghouse in cab
2. Reinstall hood, aligning with marked hinge positions
3. Reinstall batteries and connect battery cables (positive first, then negative)
4. Recharge AC system to proper specification using certified equipment
5. Check all fluid levels including engine oil, coolant, power steering, and transmission
6. Verify all electrical connections are secure and properly routed
7. Check that all hoses and lines are properly connected with no kinks or interference
8. Ensure serpentine belt is properly tensioned and routed correctly

Verification

• Prime fuel system by cycling ignition key on/off several times (listen for lift pump operation) or using manual primer on fuel filter
• Check for fuel leaks at all connections before starting engine
• Start engine and verify oil pressure rises immediately (within 5 seconds)
• Check for coolant, oil, fuel, or exhaust leaks while engine runs
• Allow engine to reach operating temperature and verify thermostat opens (upper radiator hose becomes hot)
• Check for proper cooling fan operation
• Verify AC compressor engages properly when AC is activated
• Check alternator charging (13.5-14.5 volts at battery with engine running)
• Test drive vehicle and verify normal operation, proper power delivery, and no unusual noises or vibrations
• Recheck all fluid levels after test drive
• Scan for diagnostic trouble codes and verify none are present
• Perform final inspection of engine bay for any loose connections or tools left behind

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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