Complete single piston replacement procedure for the 6.7L Cummins diesel engine, requiring cylinder head removal, piston and connecting rod assembly removal, installation of new piston, and reassembly.

Warnings

Tools required

Parts

• Piston assembly with rings and pin × 1 — Use OEM Cummins specification
• Connecting rod bearing set × 1 — Use OEM Cummins specification
• Connecting rod bolts × 2 — TTY bolts - must replace
• Cylinder head gasket × 1 — Use OEM Cummins specification
• Cylinder head bolts × 1 — TTY bolts - complete set
• Oil pan gasket × 1 — Use OEM specification
• Valve cover gasket × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Engine oil filter × 1 — Mopar 68197867AA or equivalent
• Fuel filter/water separator × 1 — Replace during major service
• Various seals and O-rings × 1 — Turbo, coolant, oil passages

Fluids

• Mopar 5W-20 Synthetic Blend — 13 qt
• Mopar OAT Coolant (Purple) — 18 qt

Preparation

1. Disconnect both battery cables (negative first, then positive) and remove batteries
2. Drain engine oil completely and remove oil filter
3. Drain cooling system into appropriate containers
4. Remove engine cover and air intake system including intercooler piping
5. Relieve fuel system pressure and disconnect fuel lines at cylinder head
6. Remove exhaust manifold and turbocharger assembly
7. Label and disconnect all electrical connectors, sensors, and wiring harnesses from cylinder head
8. Disconnect coolant hoses and oil supply/return lines
9. Remove valve cover and rocker arm assembly
10. Position engine support fixture or attach engine hoist to support engine weight
11. Ensure workspace is clean and organized with parts trays labeled by cylinder position

Procedure

1. 1

   Remove cylinder head
   Remove cylinder head bolts in reverse of tightening sequence (consult service manual for exact sequence diagram). Lift cylinder head carefully from block using lifting eyes if equipped. Place cylinder head on clean padded surface. Inspect head gasket for failure pattern to confirm affected cylinder.
   Torque spec

   Cylinder Head Bolts65 Nm (48 lb-ft)
2. 2

   Remove oil pan
   Support engine from above if not already done. Remove oil pan bolts in crisscross pattern working from ends toward center. Carefully lower oil pan, breaking gasket seal with plastic scraper if needed. Clean all gasket material from oil pan and block mating surfaces.
   Torque spec

   Oil Pan Bolts12 Nm (9 lb-ft)
3. 3

   Inspect cylinder and prepare for piston removal
   Rotate crankshaft to bring affected piston to bottom dead center (BDC). Use ridge reamer to remove any ridge at top of cylinder bore - this prevents ring breakage during piston removal. Clean metal shavings thoroughly with shop towels and vacuum. Mark connecting rod and cap with cylinder number and orientation using scribe or punch.
   ⚠Ridge reaming is critical - attempting to remove piston with ridge present will damage piston and rings.
4. 4

   Remove connecting rod cap and piston assembly
   Remove connecting rod cap bolts from the affected cylinder. Keep cap and bolts together as a set for identification (though bolts will be replaced). Carefully push piston and connecting rod assembly up and out through top of cylinder bore using wooden hammer handle. Avoid scratching cylinder wall or crankshaft journal. Place assembly on clean work surface.
   ℹ️Do not lose bearing inserts from rod and cap - examine for wear patterns indicating underlying problems.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
5. 5

   Disassemble and inspect old piston
   Remove piston pin circlips using appropriate pliers. Press or drive out piston pin to separate piston from connecting rod. Remove and discard old piston rings. Thoroughly inspect piston crown for cracks, erosion, or damage. Examine connecting rod for straightness and bearing bore condition. Inspect cylinder bore for scoring, taper, or out-of-round using bore gauge.
   ⚠If cylinder bore is damaged, scored, or out of specification, cylinder boring and honing will be required before piston installation.
6. 6

   Prepare new piston and connecting rod
   Install new connecting rod bearings into rod and cap, ensuring bearing tangs seat properly in notches. Verify bearing clearance using Plastigage on crankshaft journal - clearance should be within Cummins specification (typically 0.0015-0.0035 inches). Clean crankshaft journal and bearings thoroughly with lint-free cloth and brake cleaner. Assemble new piston to connecting rod using new piston pin, ensuring directional markings are correct (piston crown marking typically faces front of engine).
   ⚠Incorrect piston orientation will cause interference with valves and result in catastrophic engine damage.
7. 7

   Install piston rings
   Using piston ring installation tool, install rings onto new piston in correct order: oil control ring (expander and rails first), then second compression ring, then top compression ring. Verify ring end gaps are within specification using feeler gauge with ring inserted in cylinder bore. Stagger ring end gaps 120 degrees apart around piston, with no gaps aligned with piston pin bore.
   ⚠Forcing rings without proper tool will break rings. Ensure rings are oriented correctly per markings (TOP or dot facing up).
8. 8

   Install piston assembly into cylinder
   Lubricate cylinder bore, piston, and rings generously with clean engine oil. Position piston ring compressor around piston, ensuring all rings are fully compressed. Orient piston with directional marking toward front of engine. Guide connecting rod into cylinder bore and carefully tap piston into bore using wooden hammer handle on piston crown. Remove ring compressor once piston enters bore. Guide connecting rod onto crankshaft journal.
   ⚠Do not force piston - if resistance is felt, a ring may have escaped the compressor. Withdraw and restart installation.
9. 9

   Install connecting rod cap and torque
   Ensure bearing surfaces are perfectly clean and oil-lubricated. Position connecting rod cap with match marks aligned. Install NEW connecting rod bolts and hand-tighten. Torque bolts to 45 Nm (33 lb-ft) in alternating pattern. Then rotate each bolt an additional 90 degrees using torque angle gauge. Verify proper installation by rotating crankshaft - resistance should be smooth without binding.
   ⚠️TTY connecting rod bolts MUST be replaced and torqued to exact angle specification. Incorrect torque will cause bolt failure and engine destruction.
   Torque spec

   Connecting Rod Bolts45 Nm (33 lb-ft)
10. 10

    Install oil pan
    Clean oil pan and block mating surfaces thoroughly. Apply new oil pan gasket or RTV sealant per Cummins specifications. Position oil pan and install bolts finger-tight. Torque oil pan bolts to 12 Nm (9 lb-ft) in crisscross pattern from center outward. Allow sealant to cure if applicable before filling with oil.
    Torque spec

    Oil Pan Bolts12 Nm (9 lb-ft)
11. 11

    Install cylinder head
    Verify block deck and cylinder head mating surfaces are perfectly clean and free of debris. Position new cylinder head gasket on block, aligning all dowel pins and passages. Carefully lower cylinder head onto block. Install NEW cylinder head bolts and hand-tighten. Following Cummins tightening sequence, torque all bolts to 65 Nm (48 lb-ft). Then proceed with angle torquing in sequence: first pass 90 degrees, second pass 90 degrees. Verify all bolts have been angle-torqued properly.
    ⚠️Cylinder head bolt sequence and angle torque MUST be followed exactly. Incorrect procedure will result in head gasket failure and possible head warping.
    Torque spec

    Cylinder Head Bolts65 Nm (48 lb-ft)
12. 12

    Reassemble valvetrain and accessories
    Reinstall rocker arm assembly with proper torque specifications for mounting bolts and bridge adjustments. Install new valve cover gasket and torque cover bolts to 22 Nm (16 lb-ft). Reinstall fuel system components, exhaust manifold, turbocharger, and all disconnected hoses and electrical connections. Ensure all sensors are properly torqued to 15 Nm (11 lb-ft) where applicable.
    Torque spec

    Cover Bolts22 Nm (16 lb-ft)

    Sensor Bolts15 Nm (11 lb-ft)
13. 13

    Refill fluids and prime systems
    Install new oil drain plug with new crush washer torqued to 35 Nm (26 lb-ft). Install new oil filter. Fill engine with 13 quarts of Mopar 5W-20 synthetic blend oil. Refill cooling system with 18 quarts of Mopar OAT Purple coolant, bleeding air from system. Prime fuel system using lift pump or key-on cycles until firm pressure is felt at fuel filter. Check all connections for leaks.
    Torque spec

    Oil Drain Plug35 Nm (26 lb-ft)

Reassembly

1. Reinstall air intake system, intercooler piping, and engine covers
2. Reconnect both batteries (positive first, then negative)
3. Double-check all electrical connections, hoses, and fasteners for proper installation
4. Verify no tools or parts have been left in engine compartment

Verification

• Check engine oil level on dipstick and adjust if necessary
• Verify coolant level is correct and system is properly bled
• Perform visual inspection for any fluid leaks around oil pan, cylinder head, and all connections
• Start engine and listen for any abnormal noises - engine should run smoothly without knocking or unusual sounds
• Allow engine to reach operating temperature while monitoring for leaks and overheating
• Check for proper oil pressure on gauge - should read normal operating range
• Perform idle relearn procedure if required by engine control system
• Road test vehicle under light load, then gradually increase load while monitoring engine performance
• Re-check all fluid levels after test drive and inspect for any new leaks
• Monitor engine operation over next 500 miles and perform oil change at 500 miles to remove any break-in contaminants

More procedures for this vehicle