CUMMINS 3905401 OEM EXPANSION PLUG (SIDE) – RAM 5.9L/6.7L (2003–2018)

Product Description

The Cummins 3905401 OEM Expansion Plug (Side) is a genuine engine block sealing component designed for the 2003–2018 Ram 5.9L and 6.7L Cummins platform. This high-integrity steel expansion plug provides a precise interference fit to prevent coolant leaks and protect the block from long-term corrosion. Whether you're addressing a leaking freeze plug, refreshing a used engine, or completing a full rebuild, this genuine Cummins plug ensures proper cooling system sealing and durability far beyond aftermarket alternatives.

Fitment

• 2003–2007 Dodge Ram 2500/3500 with 5.9L Cummins
• 2007.5–2018 Dodge Ram 2500/3500 with 6.7L Cummins
• Side expansion/core plug location on the engine block

Cross-Reference (Cummins-Only)

For additional Cummins block sealing and hardware components, see:
• Cummins 3900625 OEM Hex Flange Head Cap Screw – Intake Heater Harness
• Cummins 3900267 OEM Tappet Cover Bolt Grommet Seal
• Cummins 3969988 OEM Intake Heater Grid Gasket – 5.9L Cummins

FAQ

What size is the Cummins 3905401 expansion plug?

This is a factory-engineered side expansion plug manufactured to precise Cummins specifications for the 5.9L and 6.7L block casting dimensions.

Is this plug used for freeze protection or sealing?

Expansion plugs serve both roles, but their primary purpose is coolant sealing. Proper fitment prevents leaks and maintains cooling system pressure.

Should expansion plugs be replaced during an engine rebuild?

Yes. Replacing all block plugs during a rebuild or refresh is recommended to avoid future coolant leaks and corrosion-related failures.

Do I need sealant when installing the 3905401 plug?

Most engine builders apply a light, coolant-safe sealant, although Cummins plugs are engineered for an interference fit. Follow OEM service procedures.

Specifications for cummins 3905401