Upper Intake Manifold with Gasket for Chevrolet Lumina (1998-1999) 3.8L

Direct-Fit Upper Intake Manifold with Gasket for 1998-1999 Chevrolet Lumina (W-Body)

What it Does: The Upper Intake Manifold with Gasket replaces the failure-prone factory plenum on the 1998-1999 Chevrolet Lumina to stop unmetered vacuum leaks and prevent catastrophic internal coolant ingestion into the cylinders.

The Stock Chevrolet Lumina Intake Plenum Degradation

The factory upper intake on the W-body Lumina equipped with the 3800 Series II L36 V6 is notorious for catastrophic structural degradation. The OEM composite nylon plenum directly interfaces with a high-temperature exhaust gas recirculation (EGR) stovepipe. Continuous thermal cycling and localized exhaust heat cook the thin polymer wall adjacent to the coolant bypass passages. Over time, the plastic softens, cracks, and erodes, introducing pressurized coolant directly into the intake tract. This thermal degradation triggers severe misfires, unmetered air intrusion, catalytic converter fouling, and catastrophic engine hydrolock if left unaddressed.

The Engineering Solution

This replacement upper intake plenum is molded from high-grade, heat-stabilized composite polymer engineered to resist prolonged thermal fatigue and chemical breakdown from fuel vapors and engine coolant. The critical runner walls and EGR interface zones feature reinforced material thickness to prevent heat sink erosion. Paired with a precision-molded port gasket utilizing vulcanized elastomeric sealing beads, this manifold creates a hermetic air-fuel seal across the lower intake base. It restores correct manifold absolute pressure (MAP) readings, stabilizes idle vacuum, and prevents coolant crossover leaks under high thermal stress.

What's Included

• 1 Upper Intake Manifold (plastic)
• 1 Upper Intake Manifold Gasket with port seals
• Fuel pressure regulator spring
• Throttle body studs
• O-rings and fittings as pictured

Technical Specifications

Compatibility

• 1998 Chevrolet Lumina 3.8L V6 Gas Naturally Aspirated
• 1999 Chevrolet Lumina 3.8L V6 Gas Naturally Aspirated

Frequently Asked Questions & Fitment Warnings

Does this fit the W-Body Lumina?

Yes, this is a direct fit for the 1998-1999 Chevrolet Lumina equipped with the 3800 Series II (L36) 3.8L engine. This kit does not fit 3.1L V6 models.

What critical steps should be followed during installation?

Fasteners must be torqued in the factory-specified sequence on a completely cool engine to ensure even gasket compression and prevent manifold ear fracture.

The Chevrolet Reliability Standard

Engineered to restore original powertrain integrity, this intake manifold assembly eliminates the primary Achilles heel of GM's legendary 3800 powerplant, ensuring sustained fuel metering accuracy and long-term operating durability.