Product Description

CUMMINS 3912086 OEM HEATER TUBE (OUTER) – 5.9L 12-VALVE (1989–1998)

The genuine CUMMINS 3912086 OEM heater tube (outer) restores correct coolant routing on 1989–1998 5.9L 12-valve Cummins engines. This metal heater tube carries engine coolant from the thermostat housing area toward the heater core and is a common replacement item on high-mileage first and second-generation Cummins trucks due to corrosion, cracking, or leakage.

Unlike generic replacements, the OEM Cummins heater tube features exact bends, mounting points, and diameter for proper coolant flow and easy installation. If your original tube is rusted, soft, or leaking at the seams, replacing it with a genuine Cummins component ensures long-term durability and factory-fit reliability.

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Key Features

• Genuine Cummins OEM construction – correct bends, length, and diameter.
• Restores proper coolant flow to the heater core.
• Direct-fit for 1989–1998 5.9L 12-valve Cummins engines.
• Corrosion-resistant materials for long service life.
• Designed to withstand vibration and thermal cycling common to 5.9L engines.

Fitment Details

• Engine: 5.9L Cummins 12-Valve (6BT)
• Years: 1989–1998
• Vehicle Applications: Dodge Ram 2500 & 3500 with 5.9L Cummins
• Notes: Used as the outer heater tube; confirm orientation and routing before ordering.

Cross-Reference & Companion Cummins Parts

CPP Diesel also stocks related coolant and heater components for the 12-valve Cummins, including:

• CUMMINS 3920405 THERMOSTAT HOUSING – 5.9L
• CUMMINS 3918033 WATER INLET – 5.9L
• CUMMINS 3283588 COOLANT BYPASS TUBE – 5.9L
• VIEW ALL GENUINE CUMMINS COOLING SYSTEM COMPONENTS

Cross-reference: 3912086, 3912086NX (reman programs may vary; verify by VIN/ESN).

Installation Notes

• Inspect heater hoses for swelling or cracks before reinstalling.
• Use fresh clamps to ensure leak-free operation.
• Clean mounting surfaces to prevent abrasion or vibration wear.
• Refill coolant and bleed air after installation.

Specifications for cummins 3912086

Frequently Asked Questions

IS THIS THE CORRECT HEATER TUBE FOR MY 12-VALVE CUMMINS?

Yes, CUMMINS 3912086 fits most 1989–1998 5.9L 12-valve trucks. Always verify routing before ordering.

WHAT IS THE DIFFERENCE BETWEEN INNER AND OUTER HEATER TUBES?

The outer tube (3912086) routes coolant toward the heater core, while the inner tube connects different coolant passages depending on model year.

SHOULD I REPLACE MY HEATER HOSES AT THE SAME TIME?

Yes—old hoses often deteriorate where they clamp to metal tubes. Replacing hoses prevents leaks and extends service life.

IS THIS A GENUINE CUMMINS PART?

Yes. CPP Diesel supplies authentic Cummins OEM components for correct fitment and long-term reliability.