Product Description
Genuine Cummins
Cummins 3905401 — Expansion Plug (Side) / Core Plug
MPN: 3905401 | Also Known As: expansion plug, core plug, cup plug (side)
Why This Part
- ✓ OE plug for sealing block passages to prevent leaks.
- ✓ Direct-fit for 2003–2018 Ram 5.9L/6.7L ISB applications (verify by VIN/ESN).
- ✓ Durable cup-style design for reliable long-term sealing.
- ✓ Stock replacement that restores factory integrity after service.
OE Fit Seals Passages 1+ Per Engine
Quick Specs
| Type | Expansion/Core Plug (cup style), side location |
|---|---|
| OE Part # | 3905401 |
| Qty Required | Varies by engine build (sold individually) |
| Use Case | Seals coolant/oil gallery openings in the block (verify location by ESN) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
| 2007.5–2018 | Ram 6.7L ISB (24V Common-Rail) | Ram 2500/3500 |
Notes: Cummins indicates 3905401 is used primarily on EPA13 6.7L ISB/QSB platforms; many Ram 5.9L/6.7L listings also carry it. Always verify by VIN/ESN.
Often Paired With
- Related expansion plug: Cummins 4938189 (freeze/core plug)
- Turbo drain plug: Cummins 3920706 (expansion plug – turbo drain)
- Fresh coolant/oil after sealing any gallery that was opened
What’s In The Box
- (1) Genuine Cummins Expansion/Core Plug (3905401)
- Sealants/gaskets not included (follow Cummins procedures for installation)
Install Tips
- Clean bore thoroughly; inspect for corrosion or damage.
- Install per Cummins spec (orientation/depth) and use approved sealant if required.
- Pressure test system after installation to confirm a proper seal.
FAQ
WILL THIS FIT MY 2003–2018 5.9L/6.7L CUMMINS RAM?Commonly listed for 2003–2018 Ram 2500/3500 with 5.9L & 6.7L ISB. Cummins notes primary usage on EPA13 6.7L ISB/QSB—always verify by VIN/ESN and location.
IS THIS THE “SIDE” CORE/EXPANSION PLUG?Yes—this is identified as a side-location cup plug used to seal block passages.
HOW MANY DO I NEED?Quantity varies by engine build and service need. Order individually based on the bores you’re servicing.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3905401 for proper fit and durability.
WHAT RELATED PLUGS SHOULD I KNOW?Common related plugs include 4938189 (freeze/core plug) and 3920706 (turbo drain expansion plug).
