Product Description
Interstate-McBee M-3921558 Oil Cooler — 1989–2002 5.9L Cummins (Aftermarket Replacement)
Direct-fit replacement engine oil cooler for the 5.9L Cummins B-Series. Restores proper oil temperature control and protects bearings, turbocharger, and valvetrain by maintaining stable lubrication temperatures. Sold individually.
- OE-style performance: Built to OE form, fit, and function for reliable cooling under towing and work loads.
- Correct fitment: Matches Cummins reference 3921558 used on B-Series 5.9L engines.
- Durable construction: Multi-plate core design for efficient heat transfer and long service life.
- Service friendly: Ideal during bearing, pump, or head work, or when oil contamination/overheating is present.
Specifications
| Brand | Interstate-McBee |
| Part Number | M-3921558 |
| OEM Reference | Cummins 3921558 |
| Sold As | Each (1 oil cooler assembly) |
| Position | Engine oil lubrication system |
What’s Included
- (1) Oil cooler assembly, P/N M-3921558
Note: Gaskets, seals, cover, and hardware are typically serviced separately. Add the correct gasket/seal kit for your engine build.
Vehicle Fitment
Always verify by engine serial number (ESN) when possible.
- 5.9L Cummins B-Series
- 12-Valve: 1989–1998 (Dodge Ram 2500/3500 and other B-Series applications)
- 24-Valve: 1998.5–2002 (Dodge Ram 2500/3500 and other B-Series applications)
Recommended/Related Parts
- Oil cooler gasket/seal kit (for your ESN)
- Oil filter and fresh engine oil
- Thermostat and coolant (if system service is due)
- Oil cooler cover and hardware (as needed)
Install Notes
- Drain coolant and engine oil; follow Cummins service procedures.
- Thoroughly clean mating surfaces; replace all seals and O-rings.
- Torque fasteners to spec in sequence; check for leaks at first start.
- If failure was due to contamination, flush the lubrication and cooling systems.
Why Buy From CPP Diesel
- ESN-verified fitment support from diesel specialists
- Fast shipping, easy returns, competitive pricing
- Deep inventory of complementary B-Series parts
FAQ
How do I confirm this fits my engine?
Match the OEM reference (Cummins 3921558) and verify with your engine serial number (ESN). Contact us if you need help confirming fitment.
Do I need a gasket/seal kit?
Yes. Always install new gaskets and O-rings when servicing the oil cooler. Choose the kit that matches your ESN.
Should I flush the system?
If the cooler failed due to debris or overheating, flush the lubrication system and replace the oil and filter after the initial run-in.
