Product Description
Cummins 3912086 — Outer Heater Tube (Near Fender) for 5.9L 12-Valve
MPN: 3912086 | Also Known As: coolant heater tube (outer), heater line | Position: Near fender (pairs with inner tube 3912087)
Why This Part
- ✓ OE formed steel tube for correct routing and firewall clearance.
- ✓ Direct-fit for 1989–1998 5.9L 12-valve Dodge/Ram Cummins.
- ✓ Restores heater performance and prevents coolant leaks from corroded lines.
- ✓ Genuine Cummins build quality and fit.
Quick Specs
| Type | Coolant heater tube (outer) |
|---|---|
| OE Part # | 3912086 |
| Material | Formed steel (OE style) |
| Qty Required | 1 per vehicle (sold individually) |
| Paired Tube | 3912087 (inner, near valve cover) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1998 | 5.9L Cummins 12-Valve (B-Series) | Dodge/Ram 2500 & 3500 |
Notes: This is the outer heater tube (nearest fender). The matching inner tube (near valve cover) is Cummins 3912087. Always verify by VIN/ESN.
Often Paired With
- Inner Heater Tube: Cummins 3912087 (near valve cover)
- Heater Hoses & Clamps: replace aged rubber and clamps during service
- Coolant: refill/bleed per factory procedure after replacement
What’s In The Box
- (1) Genuine Cummins Outer Heater Tube (3912086)
- Hoses/clamps sold separately (see “Often Paired With”).
Install Tips
- Drain coolant below tube level and cap ports to minimize spills.
- Clean mating stubs; use new clamps; route exactly as factory for clearance.
- Refill with fresh coolant and pressure-test the system; check for leaks after heat-soak.
FAQ
WILL THIS FIT MY 1989–1998 5.9L 12-VALVE CUMMINS?Yes—this is the correct outer heater tube for ’89–’98 5.9L 12-valve Dodge/Ram Cummins (verify by VIN/ESN).
IS THIS THE OUTER TUBE NEAR THE FENDER?Correct—3912086 is the outer tube (near fender). The inner companion tube near the valve cover is 3912087.
DOES IT COME WITH HOSES OR CLAMPS?No—this listing is the metal tube only. We recommend new heater hoses and clamps during installation.
IS THIS A GENUINE CUMMINS PART?Yes—genuine Cummins 3912086 for OE fit, routing, and durability.
WILL THIS FIT 24-VALVE (1998.5–2002)?No—this tube specifically targets 12-valve applications (’89–’98). Use the correct tube for 24-valve models.
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