This procedure covers the replacement of a single freeze plug (core plug) on the 6.7L Cummins diesel engine, which typically requires partial engine component disassembly to access depending on freeze plug location.

Warnings

Tools required

Parts

• Engine freeze plug (cup-style expansion plug) × 1 — Use OEM specification - size varies by location
• Permatex High-Temp RTV sealant or equivalent × 1 — Use OEM specification
• Engine coolant × 1 — Mopar OAT Purple

Fluids

• Mopar OAT Coolant (Purple) — 18 qt

Preparation

1. Verify engine is completely cold to the touch - wait at least 3 hours after last engine operation
2. Place wheel chocks behind rear wheels and engage parking brake
3. Raise front of vehicle with floor jack and secure on jack stands at frame rails
4. Remove skid plates or belly pans as necessary to access engine block from underneath
5. Locate the failed freeze plug - use inspection mirror and flashlight to identify exact position
6. Place large drain pan underneath radiator and remove lower radiator hose to drain cooling system
7. Remove radiator cap to allow system to drain more quickly
8. Identify which components must be removed for freeze plug access - common obstructions include motor mounts, accessories, brackets, or exhaust components

Procedure

1. 1

   Remove obstructing components for access
   Based on freeze plug location, remove any components blocking access. This may include: disconnecting electrical connectors, removing accessory brackets, loosening motor mount bolts, or repositioning wiring harnesses. Document all removed fasteners and their locations. For side block plugs, motor mount removal is typically required.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)

   Sensor Bolts15 Nm (11 lb-ft)
2. 2

   Support engine if motor mount removal required
   If motor mount must be removed for access, place a floor jack with wood block under the oil pan to support engine weight. Raise jack until it just contacts pan with minimal pressure - do not lift engine yet. Remove motor mount fasteners and raise engine only enough to create necessary working clearance (typically 1-2 inches).
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)
3. 3

   Remove failed freeze plug
   Using a freeze plug removal tool or slide hammer, extract the old freeze plug from the block. Alternative method: carefully punch a hole in the center of the plug with a drift punch, insert a pry bar or large screwdriver, and lever the plug out by prying against the edge. Take care not to damage the freeze plug bore in the block. If plug is severely corroded, it may come out in pieces.
   ⚠Use extreme care when prying to avoid gouging or scoring the freeze plug bore, which would prevent proper sealing of the new plug.
4. 4

   Clean and inspect freeze plug bore
   Thoroughly clean the freeze plug bore using a wire brush or rotary tool with wire wheel attachment. Remove all rust, old sealant, corrosion, and debris. The bore must be completely clean and smooth. Inspect bore for damage, cracks, or excessive corrosion. If bore is damaged, consult a machine shop for repair options. Wipe clean with shop rag and allow to dry completely.
   ℹ️The freeze plug bore must be absolutely clean and dry for proper sealant adhesion and plug retention.
5. 5

   Prepare new freeze plug
   Verify new freeze plug is correct size by test-fitting in bore - it should sit flush with slight clearance around edges before installation. Apply a thin, even bead of high-temp RTV sealant around the outer edge of the freeze plug as specified in torque specifications. Do not use excessive sealant as it will squeeze out during installation.
   Torque spec

   Freeze Plug10 Nm (7 lb-ft)
6. 6

   Install new freeze plug
   Position freeze plug in bore with cup side facing inward (convex side out). Using appropriately sized freeze plug installation driver and dead blow hammer, carefully drive plug into bore. Strike driver evenly and progressively around the circumference to ensure plug seats squarely. Drive plug until it is recessed approximately 1-2mm below the face of the block. Do not overdrive as this can distort the plug.
   ⚠Plug must be driven straight into bore. A cocked or misaligned plug will leak and require replacement.
   Torque spec

   Freeze Plug10 Nm (7 lb-ft)
7. 7

   Verify freeze plug installation
   Inspect installed freeze plug to ensure it is seated evenly around entire circumference and recessed uniformly. Check for any gaps between plug edge and block. Wipe away any excess sealant squeezed out during installation. Allow RTV sealant to cure per manufacturer instructions (typically 1 hour minimum before adding coolant).
   ℹ️Do not rush sealant cure time. Adding coolant too soon can prevent proper seal formation.
8. 8

   Reinstall removed components
   If engine was raised, carefully lower back to original position. Reinstall motor mounts, brackets, sensors, and any other components removed for access. Reconnect all electrical connectors. Torque all fasteners to specification in proper sequence. Verify all connections are secure.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)

   Sensor Bolts15 Nm (11 lb-ft)

   Cover Bolts22 Nm (16 lb-ft)

   Gasket Bolts27 Nm (20 lb-ft)
9. 9

   Refill cooling system
   Reconnect lower radiator hose. Close all drain points. Fill cooling system with Mopar OAT Purple coolant mixture (50/50 coolant to distilled water ratio). Fill radiator and reservoir to proper levels. With radiator cap off, start engine and allow to warm to operating temperature while monitoring coolant level. Add coolant as needed during burping process. Watch for leaks around new freeze plug.
   ⚠Monitor coolant temperature closely during initial warm-up. If temperature rises abnormally or leaks appear, shut down engine immediately.
10. 10

    Bleed cooling system and final inspection
    With engine at operating temperature, verify cooling system is properly bled by checking heater output and radiator fan operation. Top off coolant as needed after air purges from system. Install radiator cap. Check new freeze plug for any signs of leakage. Reinstall any belly pans or skid plates removed earlier. Lower vehicle from jack stands.
    ⚠Radiator cap must only be removed when engine is cool. Never remove cap from hot pressurized system.

Reassembly

1. Torque all reinstalled components to specifications provided - motor mount bolts are critical safety items
2. Ensure all electrical connectors are fully seated and secured with locking tabs
3. Double-check that all tools and shop rags have been removed from engine bay
4. Verify coolant reservoir is filled to COLD mark when engine is cold

Verification

• Start engine and allow to reach full operating temperature while monitoring for coolant leaks at freeze plug location
• Check coolant level after engine cools and top off if necessary - air pockets may take 24-48 hours to fully purge
• Inspect freeze plug area after 24 hours of operation for any signs of seepage or wetness
• Monitor coolant level over first week of operation - significant drop indicates leak or incomplete bleeding
• Verify heater produces full heat output and temperature gauge reads normal operating range

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