Exhaust Manifold with Catalytic Converter for Chevrolet Colorado (2004-2006) 2.8L

Direct-Fit Exhaust Manifold with Catalytic Converter for 2004-2006 Chevrolet Colorado (GMT355)

What it Does: The Exhaust Manifold with Catalytic Converter replaces the failed factory assembly on the 2004-2006 Colorado to eliminate exhaust leaks, restore accurate upstream O2 sensor readings, and maintain federal EPA emissions compliance.

The Stock Chevrolet Colorado Manifold Failure

The factory exhaust manifold on the GMT355 platform frequently succumbs to extreme thermal cycling, causing the cast material to crack along the runner seams or warp at the cylinder head flange. On the Atlas Vortec 2800 (LK5) inline-four, this failure allows ambient air to be pulled upstream of the pre-cat oxygen sensor, throwing false lean codes (such as P0171), triggering check engine lights, and forcing erratic fuel trim corrections. Unchecked thermal stress also degrades the internal ceramic substrate of the integrated converter, causing substrate breakdown, internal rattling, and restrictive backpressure.

The Engineering Solution

Engineered as a direct-fit replacement matching factory port shapes and flange geometry, this unit integrates tubular stainless steel runners and an EPA-compliant catalytic converter into a single assembly. The precision-machined, heavy-duty mounting flange ensures a flat, leak-free seal against the cylinder head, preventing cold-start ticking and exhaust intrusion into the cabin. The internal washcoat and high-flow ceramic honeycomb core guarantee complete hydrocarbon and NOx conversion while restoring factory exhaust scavenge efficiency and throttle response, directly interchanging with OEM numbers 12595160 and 12571604.

What's Included

• 1 Exhaust Manifold with Integrated Catalytic Converter
• Exhaust Manifold Gaskets
• Installation Studs and Nuts

Technical Specifications

Compatibility

• 2004 Chevrolet Colorado 2.8L L4 Base / LS / Sport / Z71 / Z85
• 2005 Chevrolet Colorado 2.8L L4 Base / LS / Sport / Sport LS / Z71 / Z71 LS / Z85 / Z85 LS
• 2006 Chevrolet Colorado 2.8L L4 LS / LT / WT / Z71 / Z71 LS / Z85

Frequently Asked Questions & Fitment Warnings

Does this fit the GMT355 Colorado?

Yes, this is a direct fit for the 2004-2006 Chevrolet Colorado equipped with the 2.8L LK5 engine. This part is EPA compliant for federal emissions vehicles only; it is not legal for sale or use on California emissions vehicles and cannot be shipped to California, Colorado, New York, or Maine.

What is the proper installation procedure to prevent future exhaust leaks?

Clean the cylinder head mating surface thoroughly, torque the included hardware evenly from the center fasteners outward, and re-torque all nuts after the initial heat cycle.

The Chevrolet Truck Standard

Midsize work trucks require sustained exhaust sealing and proper backpressure balance under continuous payload demands. This replacement manifold restores factory structural integrity and eliminates exhaust leaks, preserving low-end torque for reliable hauling and daily fleet duty.