Product Description
Interstate-McBee M-3959574 Piston Cooling Plug (Oil Squirter) – 2003–2018 5.9L & 6.7L Cummins ISB
Direct-replacement piston cooling plug (oil squirter / nozzle) for 2003–2018 Cummins ISB 5.9L and 6.7L engines. This jet directs pressurized oil to the underside of the piston crown to control temperature and improve durability. Sold individually.
- OE-style fit: Matches Cummins reference 3959574.
- Durable build: Quality aftermarket replacement from Interstate-McBee.
- Restore performance: Replaces clogged, damaged, or leaking piston cooling nozzles.
Specifications
| Brand | Interstate-McBee |
| Part Number | M-3959574 |
| OEM Reference | Cummins 3959574 |
| Function | Piston cooling plug / oil squirter nozzle |
| Sold As | Each (1 nozzle) |
| Typical Qty Required | 6 per engine (one per cylinder) — verify by ESN |
| Position | Crankcase / block, oil gallery to cylinder cooling jet |
Vehicle/Engine Fitment
Always confirm by engine serial number (ESN) and parts catalog for your specific application.
- Dodge Ram 2500/3500 with Cummins ISB 5.9L (2003–2007)
- Dodge/Ram 2500/3500 with Cummins ISB 6.7L (2007.5–2018)
- Ram 4500/5500 chassis cab with Cummins ISB 6.7L (select years in this range)
- Other ISB/QSB applications where Cummins 3959574 is specified
What’s Included
- (1) Piston cooling plug / oil squirter, P/N M-3959574
Recommended/Related Parts
- Oil gallery seals / O-rings for the cooling plug (as applicable to your block)
- Engine oil filter and fresh oil (recommended after internal oiling work)
- Complementary bottom-end service parts (rod/main bearings, piston rings, etc.)
Install Notes
- Work clean: debris in the oil gallery can clog the nozzle. Clean and blow out galleries before installation.
- Inspect nozzle orifice and check ball (if equipped) for damage or blockage; replace as needed.
- Follow the Cummins service manual for orientation, seating depth, and torque specs for your ESN.
- After assembly, prime the oiling system and verify oil pressure on first start.
FAQ
How many do I need?
Most ISB 5.9L/6.7L engines use six — one per cylinder. Confirm by ESN and parts catalog for your specific block.
What symptoms indicate a bad cooling plug?
Overheated pistons, scuffing, or detonation damage; metal debris clogging the nozzle; or physical damage discovered during teardown.
Do I need new seals?
If your application uses seals or crush washers, replace them. Reusing old seals can cause leaks or pressure loss.
