The SPOOLOGIC Exhaust Manifold & Turbo Install Kit SL-300-070 is the complete gasket-and-O-ring kit for the exhaust manifold and factory turbo on 1989-1998 5.9L Cummins 12-Valve Dodge Ram trucks — everything you'll touch when the manifold or turbo comes off, in one box. Six exhaust manifold gaskets, multi-layer steel turbo flange gasket, oil drain line gasket, Viton O-rings for the oil feed and oil drain lines, and the compressor housing outlet O-ring. Backed by a 1-Year Limited Warranty.

Every part in this kit is single-use by design. MLS gaskets crush down to the exact roughness of the flange on first torque, Viton O-rings take a permanent compression set the moment you install them, and per-cylinder manifold gaskets seat to the head at torque and can’t seat a second time. Reusing any of them is the #1 cause of post-job leaks — that’s why we built the kit around one-and-done, install-it-right sealing hardware.

Common Exhaust Manifold & Turbo Failure Symptoms

• Ticking or hissing at idle — reused per-cylinder exhaust manifold gasket that already crushed on the previous install, leaking exhaust at the port.
• Exhaust leak at the turbo flange — reused MLS turbo mounting gasket that lost its crushed profile after removal.
• Oil weeping onto the turbo housing — oil feed or oil drain O-rings that took a compression set and can’t seal engine oil at temperature.
• Boost leak or slow spool — reused compressor housing outlet O-ring that can’t seal the charge-air path.

Why You Replace All of This — Not Just the One That’s Leaking

Exhaust manifold and turbo gaskets and O-rings are not designed to be reused. Here’s what’s actually happening to the parts you’re tempted to put back:

• Exhaust manifold gaskets — the 5.9L 12V uses six individual port gaskets, one per cylinder, that seal each exhaust port to the manifold. Once torqued they crush down to the surface roughness of the head and manifold. Reuse one and you get a port leak that ticks at idle and chews soot into the manifold-to-head joint.
• Multi-layer steel turbo flange gasket — thin steel layers bonded with an elastomer coating. On first torque-up the layers crush down to mate the exact surface roughness of the turbo and manifold flanges. Once crushed they cannot crush again to a new surface. Reused MLS gaskets are the #1 cause of post-job exhaust leaks at the turbo.
• Oil drain line gasket — the turbo center section drains back to the pan under almost no pressure but at full crankcase oil temperature. Reuse it and you get an oil weep that drips on the turbo housing and smokes.
• Oil drain and oil feed O-rings — rubber O-rings take a permanent compression set after the first install. Used O-rings can’t spring back to the original cross-section, so they leak oil onto a hot turbo — that’s how engine fires start.
• Compressor housing outlet O-ring — seals the charge-air path between the compressor housing and the intake plumbing. A used O-ring here leaks boost, which costs you EGT and fuel economy and eventually melts.

Component Breakdown — What Each Piece Seals

• 6 exhaust manifold gaskets — one per cylinder, sealing each exhaust port to the manifold across all six cylinders.
• 1 turbo flange gasket — multi-layer steel gasket that seals the turbo to the exhaust manifold. Sees full exhaust gas temperature and pressure.
• 1 oil drain line gasket — seals the oil drain line where it bolts to the block. Lives at full crankcase oil temperature.
• 1 oil drain line O-ring — seals the oil drain line where it enters the turbo center section.
• 2 oil feed line O-rings — seal the oil feed line at the block and the turbo center section. Pressurized engine oil at full temperature.
• 1 compressor housing outlet O-ring — seals the charge-air outlet between the compressor housing and the intake plumbing.

Material Technology — Why Each Material Was Chosen

• Multi-layer steel construction — both the exhaust manifold gaskets and the turbo flange gasket are MLS, not composite. MLS uses three or more thin steel layers with an elastomer coating, each layer free to flex independently as the joint grows and shrinks with heat. This is the construction that survives 1,200°F+ exhaust gas temperatures.
• Viton (FKM) O-rings — the oil-side and charge-air O-rings are Viton, not standard nitrile. Viton holds its compression set and chemical resistance against hot engine oil and hot charge air far longer than nitrile, which is what fails on the cheap reuse-kit O-rings.

Install Notes

• Do not reuse any gasket or O-ring in this kit — every piece is single-use by design.
• Clean every mating surface before installing the new gaskets and O-rings. MLS gaskets cannot bridge over carbon deposits, machining burrs, or old gasket material. A razor scraper and brake clean is the minimum.
• Lightly oil the O-rings with clean engine oil before installing, so they seat without rolling or tearing.
• Pre-fill the turbo with clean oil through the oil feed port before cranking. Dry-starting a turbo eats the journal bearing on the first revolution.
• Inspect the exhaust manifold itself for cracks at the ports or flange before reinstalling — the 5.9L 12V manifold is known to crack and a cracked manifold will leak past any gasket.
• Follow the Cummins service manual torque specs and sequence for the exhaust manifold bolts, the turbo mounting nuts, the oil feed banjo, and the oil drain bolts.

Features

• Complete exhaust manifold and turbo install kit for 1989-1998 5.9L Cummins 12-Valve
• Six per-cylinder exhaust manifold gaskets
• Multi-layer steel turbo flange gasket
• Viton O-rings on the oil feed, oil drain, and compressor outlet
• Backed by a 1-Year Limited Warranty

What’s Included

• 6 exhaust manifold gaskets
• 1 turbo flange gasket
• 1 oil drain line gasket
• 1 oil drain line O-ring
• 2 oil feed line O-rings
• 1 compressor housing outlet O-ring

Fits 1989-1998 5.9L Cummins 12-Valve

• 1989 – 1998 Dodge Ram 2500 3500 5.9L Cummins 12-Valve

Turbo Applications

This install kit fits the following factory turbochargers:

• Holset H1C (1989-1993 5.9L Cummins 12-Valve)
• Holset HX35 (1994-1998 5.9L Cummins 12-Valve)

Replaces Factory OEM Part Numbers

• Cummins: 3902477 — exhaust manifold gasket (5.9L 12V, per cylinder)
• Cummins: 3901356 — turbo flange / mounting gasket
• Cummins: 3937706 — turbo oil drain gasket
• Cummins: 5264569 — turbo oil drain gasket (later revision)
• BD Diesel: 3545575 — 5.9L Holset turbo mounting gasket kit

1-Year Limited Warranty

Every SPOOLOGIC Exhaust Manifold Turbo Install Kit is covered by a 1-Year Limited Warranty against defects in materials and workmanship for the original purchaser. To initiate a warranty claim, the kit must first be shipped back to SPOOLOGIC at the customer’s expense for inspection. If SPOOLOGIC determines the kit is defective in materials or workmanship, a replacement will be shipped at SPOOLOGIC’s cost. Warranty does not cover labor, downtime, towing, consequential damages, failures caused by improper installation, failures caused by dirty or damaged mating surfaces, reuse of any kit component, or use outside the listed fitment.