Engine Rebuild

Complete engine rebuild of the 5.9L Cummins diesel engine including disassembly, inspection, machining as needed, and reassembly with new bearings, gaskets, seals, and wear components.

Warnings

Tools required

Parts

• Complete gasket set (head, oil pan, valve cover, all seals) × 1 — Use OEM specification
• Cylinder head gasket × 1 — Use OEM specification
• Main bearing set (standard or oversized as measured) × 1 — Use OEM specification
• Rod bearing set (standard or oversized as measured) × 1 — Use OEM specification
• Piston ring set (6 cylinders) × 1 — Use OEM specification
• Timing gear set (or chain/sprocket depending on variant) × 1 — Use OEM specification
• Oil pump (or rebuild kit) × 1 — Use OEM specification
• Water pump × 1 — Use OEM specification
• Thermostat and housing gasket × 1 — Use OEM specification
• Valve stem seals (12 piece) × 1 — Use OEM specification
• Camshaft (if worn beyond spec) × 1 — Use OEM specification
• Lifters/tappets (12 piece set) × 1 — Use OEM specification
• Front and rear crankshaft seals × 1 — Use OEM specification
• Camshaft seal × 1 — Use OEM specification
• Oil filter × 1 — Use OEM specification
• Fuel filter (primary and secondary) × 1 — Use OEM specification
• Injector O-ring and seal kit × 1 — Use OEM specification
• Rod bolts (if reusing rods) × 1 — Use OEM specification
• Head bolts (TTY type) × 1 — Use OEM specification
• Main cap bolts (TTY type) × 1 — Use OEM specification
• Connecting rod bolts (TTY type) × 1 — Use OEM specification
• Engine assembly lube × 1 — Use OEM specification
• Thread sealant (for coolant passages) × 1 — Use OEM specification
• Anti-seize compound × 1 — Use OEM specification
• RTV silicone gasket maker × 1 — Use OEM specification

Fluids

• 15W-40 diesel engine oil — 12 qt
• Ethylene glycol 50/50 coolant — 28 qt

Preparation

1. Drain all fluids (engine oil, coolant, fuel) into appropriate containers
2. Disconnect both batteries (negative terminals first)
3. Remove hood for clearance
4. Relieve fuel system pressure by loosening fuel filter drain valve
5. Disconnect all electrical connectors, labeling each one
6. Remove radiator, intercooler, and all cooling system hoses
7. Disconnect exhaust system at turbocharger outlet
8. Remove intake air plumbing and air filter housing
9. Disconnect fuel lines at injection pump and lift pump
10. Remove transmission (manual or automatic) from engine
11. Disconnect all vacuum lines and breather hoses
12. Attach engine hoist to factory lifting points on block
13. Support engine weight and remove motor mounts
14. Carefully extract engine from vehicle and mount on heavy-duty engine stand
15. Set up clean workspace with parts washer and organization bins

Procedure

1. 1

   Remove external components and accessories
   Remove turbocharger, exhaust manifold, intake manifold, fuel injection pump, alternator, power steering pump, A/C compressor (if equipped), water pump, thermostat housing, and all external brackets. Remove valve cover, exposing camshaft and rocker assembly. Label and photograph all fuel injector positions before removal.
2. 2

   Remove timing cover and set timing marks
   Remove harmonic balancer using puller (do not hammer). Remove timing gear housing bolts in reverse of tightening sequence. Before removing timing gears, mark the timing position of the crankshaft gear to the camshaft gear with a paint marker (this engine uses a gear-driven timing train, not a chain). Install timing pin through camshaft gear if available to lock position. Document gear tooth alignment and keyway positions with photos.
   Torque spec

   Crankshaft Pulley Bolt180 Nm (133 lb-ft)

   Timing Cover Bolts - 8mm25 Nm (18 lb-ft)
3. 3

   Remove camshaft and valve train
   Remove rocker lever assemblies and push rods (keep in order). The cam followers/tappets ride in the block and are removed after the camshaft is withdrawn; keep them in order with labels. The camshaft is located in the block (cam-in-block/OHV design) and rides in pressed-in cam bearings. After removing the cam gear, carefully withdraw the camshaft out the front of the block, supporting it to avoid bearing journal damage. There are no camshaft bearing caps to remove. Remove timing gear from camshaft. Store all components in labeled containers maintaining installation order.
   Torque spec

   Camshaft Bearing Cap Bolts14 Nm (10 lb-ft)
4. 4

   Remove cylinder head
   Loosen cylinder head bolts in reverse of tightening sequence (work from outside toward center). Remove cylinder head and place on clean padded surface. Remove and discard head gasket. Clean all carbon deposits from combustion chambers. Inspect head for cracks using dye penetrant or magnaflux. Measure head flatness with straight edge and feeler gauge (maximum warp 0.004 inch). If beyond spec, head must be resurfaced by machine shop.
   Torque spec

   Cylinder Head Bolts65 Nm (48 lb-ft)
5. 5

   Remove oil pan and oil pump
   Remove oil pan bolts in reverse sequence. Remove oil pan and gasket. Remove oil pump pickup tube and screen assembly. Remove oil pump mounting bolts and extract pump assembly. Inspect pump gears for wear and measure clearances. Replace pump if clearances exceed specification (typically 0.004-0.010 inch).
   Torque spec

   Oil Pan Bolt12 Nm (9 lb-ft)

   Oil Pump Bolts12 Nm (9 lb-ft)

   Oil Pump Pickup Tube12 Nm (9 lb-ft)
6. 6

   Remove pistons and connecting rods
   Rotate crankshaft to position piston at bottom dead center. Use ridge reamer to remove ridge at top of cylinder bore (prevents ring damage during removal). Mark each connecting rod and cap with cylinder number using number stamps. Remove connecting rod cap bolts. Remove cap and push piston/rod assembly out top of block using wooden dowel or hammer handle. Keep pistons, rods, and caps matched and labeled by cylinder number.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
7. 7

   Remove crankshaft and main bearings
   Mark main bearing caps with number stamps (should already be marked from factory). Remove main bearing cap bolts in sequence working from outside caps toward center. Carefully remove main caps, keeping them in order. Lift crankshaft out of block. Remove all bearing shells from caps and block, keeping upper and lower shells matched by journal number. Inspect crankshaft journals for scoring, out-of-round, and taper using micrometer.
   Torque spec

   Main Bearing Cap Bolts75 Nm (55 lb-ft)
8. 8

   Disassemble and inspect cylinder head
   Using a valve spring compressor (pushrod/OHV cylinder head type), compress springs and remove keepers for each valve. Remove retainers, springs, and valves, keeping all components organized by cylinder and position (intake/exhaust). Remove valve stem seals. Measure valve stem diameter and valve guide clearance. Check valve face and seat condition. Measure valve spring free height and installed height. Head should be sent to machine shop for valve job, seat cutting, guide replacement if needed, and pressure testing.
9. 9

   Measure and inspect all components
   Measure cylinder bores for out-of-round and taper using dial bore gauge. Measure all crankshaft journals (main and rod) with micrometer. Measure connecting rod big end bore and small end bore. Check piston-to-cylinder wall clearance. Measure piston ring end gap in cylinder bore. Inspect camshaft lobes and bearing journals. Check deck surface flatness. All measurements must be within factory specification or components must be machined or replaced. Block may require boring and honing for oversized pistons if cylinders are worn beyond spec.
10. 10

    Machine shop work and final cleaning
    Send block to machine shop for hot tank cleaning, magnetic particle inspection, cylinder boring/honing as needed, deck resurfacing if required, and line boring if bearing bores are out of spec. Send crankshaft for inspection, polishing, and undersize grinding if needed. Send cylinder head for valve job, pressure testing, and resurfacing. Send connecting rods for reconditioning, resize, and new bushing installation if needed. Upon return, final clean all components with solvent and compressed air, ensuring all oil passages are clear.
11. 11

    Install main bearings and crankshaft
    Install upper main bearing shells into block, ensuring bearing tabs engage notches. Lubricate bearing surfaces with assembly lube. Carefully lower crankshaft into block. Install lower bearing shells into main caps. Apply assembly lube to lower bearings. Install main caps in correct order and orientation (marked numbers face same direction). Install NEW main cap bolts and torque per Cummins service manual specification (verify exact multi-step torque-plus-angle values for this engine before assembly). Verify crankshaft rotates freely. Check bearing clearance using Plastigage (should be 0.0015-0.0035 inch for mains).
    ⚠Main cap bolts are torque-to-yield and must be replaced with new bolts. Do not reuse old bolts.
    Torque spec

    Main Bearing Cap Bolts75 Nm (55 lb-ft)
12. 12

    Install pistons and connecting rods
    Install piston rings on pistons using ring expander tool. Ensure ring end gaps are staggered 120 degrees apart. Oil ring expander gap should not align with pin bore. File ring end gaps if needed to achieve 0.010-0.020 inch gap. Install rod bearings in connecting rods and caps, lubricate with assembly lube. Install piston/rod assembly into correct cylinder using piston ring compressor. Ensure directional markings on piston face forward (toward front of engine). Tap piston gently down bore. Install rod cap with NEW rod bolts. Torque rod bolts per Cummins service manual specification (verify exact torque-plus-angle values, which differ between 12-valve and 24-valve rod designs, before assembly). Verify bearing clearance with Plastigage (0.0015-0.003 inch). Repeat for all six cylinders.
    ⚠Connecting rod bolts are torque-to-yield and must be replaced. Ring compressor must fully compress rings or cylinder bore damage will occur.
    Torque spec

    Connecting Rod Bolts45 Nm (33 lb-ft)
13. 13

    Install oil pump and oil pan
    Install new or rebuilt oil pump with NEW gasket. Torque oil pump bolts to 12 Nm (9 ft-lb). Prime oil pump by filling pump cavity with clean engine oil and rotating pump drive shaft. Install oil pump pickup tube with new O-ring, torque to 12 Nm (9 ft-lb). Clean oil pan mating surface thoroughly. Apply thin bead of RTV sealant to pan rail and install new oil pan gasket (or gasket per manufacturer instruction). Install oil pan and torque bolts in sequence starting at center and working outward to 12 Nm (9 ft-lb). Allow RTV to cure 1 hour before adding oil.
    Torque spec

    Oil Pump Bolts12 Nm (9 lb-ft)

    Oil Pump Pickup Tube12 Nm (9 lb-ft)

    Oil Pan Bolt12 Nm (9 lb-ft)
14. 14

    Reassemble cylinder head valvetrain
    Install NEW valve stem seals on guides using seal driver. Lubricate valve stems with assembly lube. Install valves into guides in original positions. Install valve springs with closer-wound coils toward head. Install retainers and compress springs with valve spring compressor. Install keepers, ensuring they seat properly in valve stem groove. Tap valve stem lightly with plastic hammer to seat keepers. Verify all keepers are properly installed before releasing spring pressure. Machine shop should have verified all valve spring installed heights and pressures during head reconditioning.
15. 15

    Install cylinder head
    Clean block deck surface and cylinder head mating surface with gasket scraper and solvent. Ensure surfaces are completely clean and dry. Check that all head bolt holes are clean and dry (oil in holes can cause false torque readings). Install NEW head gasket with orientation marks facing up (TOP or OBEN marking). Do not use any sealant on head gasket. Carefully lower cylinder head onto block, aligning dowel pins. Install NEW head bolts with light coat of clean engine oil on threads. Torque head bolts in the proper factory sequence using the multi-stage torque procedure specified by Cummins for this engine (12-valve and 24-valve procedures differ; verify exact staged torque-plus-angle values before assembly).
    ⚠Cylinder head bolts are torque-to-yield and must be replaced. Never reuse old head bolts on Cummins diesel engines.
    Torque spec

    Cylinder Head Bolts65 Nm (48 lb-ft)
16. 16

    Install camshaft and valve train
    Lubricate camshaft lobes and bearing journals with assembly lube. Install camshaft timing gear onto camshaft with key and keyway aligned. Carefully slide camshaft into block, supporting shaft to avoid bearing damage. Align timing marks on camshaft gear with crankshaft gear per factory timing marks (or use timing pin). Slide the camshaft into the block and secure it with the camshaft thrust plate at the front of the block, torquing the thrust plate bolts to specification. There are no camshaft bearing caps on this engine. Install lifters/tappets in original bores with assembly lube. Install pushrods in original positions. Adjust valve lash per factory specification for the specific engine variant (12-valve engines typically 0.010 inch intake / 0.020 inch exhaust; 24-valve engines use different values—verify against Cummins service manual).
    Torque spec

    Camshaft Bearing Cap Bolts14 Nm (10 lb-ft)
17. 17

    Install timing cover and front accessories
    Install new front crankshaft seal in timing cover using seal driver. Clean timing cover mating surface and block surface. Apply thin bead of RTV sealant to cover corners where oil pan meets block. Install timing cover with new gasket. Torque timing cover bolts in sequence to 25 Nm (18 ft-lb) for 8mm bolts. Install the harmonic balancer/vibration damper onto the crankshaft, aligning it to the crankshaft register/dowel as designed. Clean balancer bolt threads and apply thread locker. Torque crankshaft pulley/damper bolt to the Cummins-specified value using a calibrated torque wrench (do not use an impact wrench for final torque); verify exact torque-plus-angle spec before assembly. Install water pump with new gasket, torque mounting bolts to 47 Nm (35 ft-lb).
    Torque spec

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

    Crankshaft Pulley Bolt180 Nm (133 lb-ft)

    Sensor Mounting Bolts11 Nm (8 lb-ft)
18. 18

    Install external components
    Install fuel injection pump with new gasket, ensuring timing marks align properly. Install injectors with NEW O-rings and copper sealing washers. Torque injector hold-down bolts per specification. Install exhaust manifold with NEW studs and nuts, apply anti-seize to threads. Torque exhaust manifold nuts to 30 Nm (22 ft-lb) working from center outward. Install intake manifold with new gasket, torque bolts to 25 Nm (18 ft-lb). Install turbocharger with new gasket. Install valve cover with new gasket, torque bolts in sequence to 10 Nm (7 ft-lb). Install all accessories (alternator, power steering pump, A/C compressor) and belt tensioners.
    Torque spec

    Exhaust Manifold Nuts30 Nm (22 lb-ft)

    Intake Manifold Bolt25 Nm (18 lb-ft)

    Valve Cover Bolts10 Nm (7 lb-ft)
19. 19

    Final assembly and installation
    Install flywheel (or flexplate) with new bolts using thread locker. Torque flywheel bolts to 95 Nm (70 ft-lb) in star pattern. Install rear main seal using seal driver. Install oil drain plug with NEW crush washer, torque to 35 Nm (26 ft-lb). Pre-fill oil filter with clean engine oil. Install new oil filter. Fill engine with 15W-40 diesel engine oil to the capacity specified for your model year (approximately 12 quarts with filter—verify against the owner's/service manual and check the dipstick). Reinstall engine in vehicle using hoist and install motor mounts, torque mount bolts to specification. Reconnect transmission. Reconnect all wiring harnesses, fuel lines, cooling hoses, exhaust system, and vacuum lines. Install new fuel filters. Fill the cooling system with the correct 50/50 coolant for your model year (conventional ethylene glycol for earlier years, HOAT for later models per Chrysler spec) to the specified capacity—verify exact capacity against the service manual.
    Torque spec

    Flywheel Bolts95 Nm (70 lb-ft)

    Oil Drain Plug35 Nm (26 lb-ft)
20. 20

    Initial startup and break-in
    Prime the oil system by cranking the engine with fueling/starting disabled (method varies by injection system—use the appropriate no-start crank procedure for your pump variant) until oil pressure registers on the gauge. Reconnect fuel solenoid. Bleed air from fuel system at filter housing and injector return lines. Check for any fuel, oil, or coolant leaks before starting. Start engine and verify oil pressure immediately (should be 10+ PSI at idle when warm). Allow engine to idle for 20 minutes, monitoring for leaks and unusual noises. Check and adjust valve lash after 20 minute warm-up if needed. Vary engine speed between 1500-2500 RPM for next 30 minutes. Perform initial oil and filter change at 500 miles. Avoid high loads and sustained high RPM for first 1000 miles during ring seating period.
    ⚠Do not exceed 2500 RPM or apply heavy loads during initial 1000 mile break-in period. Rings must properly seat to cylinder walls.

Reassembly

1. All torque-to-yield fasteners (head bolts, main cap bolts, rod bolts) must be replaced with new hardware
2. Follow proper torque sequences for all critical components - refer to torqueRefs in each step
3. Use Plastigage to verify bearing clearances before final assembly
4. Apply assembly lube to all rotating components during installation
5. Ensure timing marks are properly aligned before installing timing cover
6. Prime oil system before initial startup to prevent bearing damage
7. Use new gaskets and seals throughout - do not reuse any sealing components
8. Allow RTV sealant to cure per manufacturer instructions before filling with fluids

Verification

• Verify oil pressure reaches 10+ PSI at idle and 30-60 PSI at 2000 RPM when warm
• Check for any oil, fuel, or coolant leaks after initial startup and 20 minute warm-up
• Verify no unusual engine noises (knocking, ticking, grinding)
• Confirm proper engine operating temperature (185-205°F)
• Check valve lash after initial warm-up and adjust if needed
• Verify charging system voltage (13.5-14.5V with engine running)
• Road test vehicle under light load, confirming smooth operation and proper power delivery
• Perform compression test after break-in period - all cylinders should be within 10% of each other (typically 350-400 PSI)
• Change oil and filter at 500 miles, inspect for metal particles in old oil
• Re-torque cylinder head bolts after 500 miles if specified by manufacturer (check service manual)
• Monitor oil consumption during break-in - should stabilize after 1000 miles

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