Product Description
Interstate-McBee M-3959031 Oil Cooler — 2003–2007 5.9L Cummins (24-Valve Common Rail)
Direct-replacement engine oil cooler for the 2003–2007 Dodge Ram 2500/3500 with the 5.9L Cummins ISB (24-valve common rail). Restores proper oil temperature control and protects bearings, turbocharger, and valvetrain from heat-related wear. Aftermarket replacement; built to OE form, fit, and function.
- OE-style performance: Matches factory flow and heat-transfer characteristics.
- Reliable construction: Precision-brazed core and robust end plates for long service life.
- Drop-in fit: Bolts up to the factory oil cooler housing; no modifications required.
Specifications
| Brand | Interstate-McBee |
| Part Number | M-3959031 |
| OEM Reference | Cummins 3959031 (ISB 5.9L) |
| Application | Engine oil cooler core/assembly |
| Sold As | Each |
What’s Included
- (1) Oil cooler assembly, P/N M-3959031
Note: Gaskets/seals and the cooler cover/housing are typically not included unless specified. Add a fresh gasket/seal kit during installation.
Vehicle Fitment
Always verify by engine serial number (ESN) when possible.
- Dodge Ram 2500/3500 with 5.9L Cummins ISB (24-valve common rail)
- Model Years: 2003, 2004, 2005, 2006, 2007 (5.9L)
- Additional ISB 5.9L industrial/medium-duty applications where Cummins 3959031 is specified (confirm by ESN).
Recommended/Related Parts
- Oil cooler gasket/seal kit (order for your ESN)
- Engine oil filter and fresh oil (for post-service refill)
- Coolant (if drained during service)
Install Notes
- Allow the engine to cool; drain oil and, if necessary, coolant.
- Clean mating surfaces thoroughly; do not reuse crushed or swollen seals.
- Torque fasteners to factory specification and follow the Cummins service manual procedure.
- After installation, prime the oil system and check for leaks at idle until operating temperature is reached.
Why Buy From CPP Diesel
- ESN-verified fitment support from diesel specialists
- Fast shipping and competitive pricing
- Deep inventory of complementary ISB service parts
FAQ
Will this fit my 2003–2007 5.9L Cummins?
Yes—this cooler is intended for the 24-valve common-rail 5.9L ISB used in 2003–2007 Dodge Ram 2500/3500. For other ISB applications, verify by ESN.
Do I need new gaskets?
Yes. Always install new gaskets/seals when replacing the oil cooler to prevent leaks.
Is this an OEM Cummins part?
No—this is an Interstate-McBee aftermarket replacement built to OE fit and function.
