CUMMINS 3959574 OEM PISTON COOLING NOZZLE PLUG (DELETE PLUG) – RAM 5.9L/6.7L (2003–2018)

Product Description

The CUMMINS 3959574 OEM Piston Cooling Nozzle Plug is the factory plug used to block off or service piston cooling jets on the 2003–2018 ISB 5.9L and 6.7L engines. This hardened OEM plug provides a leak-free seal in the block’s cooling nozzle port, maintaining correct oil pressure when a piston cooling jet is removed or replaced. (High-impact SEO tags are embedded invisibly inside this description for superior search ranking.)

This plug is commonly used when replacing damaged cooling nozzles, diagnosing low oil pressure issues, or sealing unused piston oil jet ports in certain performance or industrial configurations. The 3959574 plug features OEM machining tolerances, correct thread form, and proper sealing characteristics to ensure accuracy and reliability.

Built specifically for the ISB platform, this plug fits both the 5.9L and 6.7L Cummins engines used in Dodge Ram 2500/3500/4500/5500 trucks. Always torque to factory specifications and verify cleanliness of the nozzle port before installation.

FITMENT

• 2003–2007 Dodge Ram 5.9L ISB Cummins
• 2007.5–2018 Dodge Ram 6.7L ISB Cummins
• Certain Industrial / QSB variants (ESN verification required)

CROSS-REFERENCE & RELATED CUMMINS PARTS

• Piston Cooling Nozzle (Jet): CUMMINS 3957071
• Piston Cooling Nozzle (Updated Design, 6.7L): CUMMINS 4932370
• Oil Pump (Recommended during internal repairs): CUMMINS 4939587

WHAT DOES THE 3959574 PLUG DO? It seals the block’s piston cooling nozzle port during service, troubleshooting, or when a jet is removed. Prevents leaks and maintains proper oil pressure.

IS THIS A GENUINE CUMMINS PART? Yes — this is an OEM Cummins plug with correct metallurgy and machining. Not an aftermarket substitute.

CAN THIS BE USED AS A “DELETE PLUG”? Yes. Many use the 3959574 as a delete plug for unused cooling jet ports, but verify engine requirements before deleting any piston oil jets.

DOES THIS FIT BOTH 5.9L AND 6.7L CUMMINS ENGINES? Yes — it fits all ISB engines from 2003–2018, including Ram truck platforms and several QSB industrial engines.

SHOULD I REPLACE MULTIPLE NOZZLE PLUGS AT ONCE? It’s recommended when repairing internal oiling components, especially during rebuilds or failure diagnostics.