1. Introduction
This manual provides detailed instructions for the installation, operation, maintenance, and troubleshooting of your Dorman 674-391 Driver Side Exhaust Manifold Kit. This precision-engineered and durably manufactured exhaust manifold is designed to match the fit and function of the original manifold on specified vehicles, ensuring reliable performance and a complete repair.
Image: Dorman Exhaust Manifold Kit, highlighting components for a complete repair.
2. Vehicle Compatibility
The Dorman 674-391 Driver Side Exhaust Manifold Kit is compatible with the following vehicles. Always confirm fitment using your vehicle's make, model, and trim level before installation.
- Chevrolet C2500 Suburban: 1996, 1997, 1998, 1999
- Chevrolet C2500: 1996, 1997, 1998, 1999, 2000
- Chevrolet C3500: 1996, 1997, 1998, 1999, 2000
- Chevrolet C3500HD: 1996, 1997, 1998, 1999, 2000
- Chevrolet Express 3500: 1996, 1997, 1998, 1999, 2000
- Chevrolet K2500 Suburban: 1996, 1997, 1998, 1999
- Chevrolet K2500: 1996, 1997, 1998, 1999, 2000
- Chevrolet K3500: 1996, 1997, 1998, 1999, 2000
- Chevrolet P30: 1996, 1997, 1998, 1999
- GMC C2500 Suburban: 1996, 1997, 1998, 1999
- GMC C2500: 1996, 1997, 1998, 1999, 2000
- GMC C3500: 1996, 1997, 1998, 1999, 2000
- GMC C3500HD: 1996, 1997, 1998, 1999, 2000
- GMC K2500 Suburban: 1996, 1997, 1998, 1999
- GMC K2500: 1996, 1997, 1998, 1999, 2000
- GMC K3500: 1996, 1997, 1998, 1999, 2000
- GMC Savana 3500: 1996, 1997, 1998, 1999, 2000
3. What's Included
Your Dorman 674-391 Driver Side Exhaust Manifold Kit includes the following components for a complete repair:
- 1 x Dorman Driver Side Exhaust Manifold
- Required Gaskets (for manifold to cylinder head and manifold to downpipe)
- Required Downpipe Hardware (bolts, nuts, studs)
Image: All components of the Dorman 674-391 Driver Side Exhaust Manifold Kit.
4. Safety Information
WARNING: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm.
Always prioritize safety when working on your vehicle. Professional installation is recommended. If performing installation yourself, adhere to the following safety guidelines:
- Wear appropriate personal protective equipment (PPE), including safety glasses, gloves, and hearing protection.
- Ensure the vehicle is securely supported on jack stands or a lift before working underneath.
- Allow the engine and exhaust system to cool completely before beginning work to prevent burns.
- Disconnect the vehicle's battery before starting any electrical work or major component removal.
- Work in a well-ventilated area to avoid inhaling exhaust fumes or other hazardous vapors.
- Use the correct tools for each step to prevent injury and damage to components.
5. Installation Guide
This section outlines the general steps for replacing an exhaust manifold. Specific procedures may vary by vehicle model. Refer to your vehicle's service manual for precise torque specifications and detailed instructions.
5.1. Preparation
- Park the vehicle on a level surface and engage the parking brake.
- Allow the engine to cool completely.
- Disconnect the negative terminal of the battery.
- Raise the vehicle safely using a lift or jack stands.
- Locate the driver side exhaust manifold.
5.2. Removal of Old Manifold
- If applicable, disconnect any oxygen sensors or other components attached to the manifold.
- Remove the bolts connecting the exhaust downpipe to the manifold.
- Remove the bolts securing the manifold to the cylinder head. These may be seized due to heat and corrosion; use penetrating oil if necessary.
- Carefully remove the old exhaust manifold and any old gaskets.
- Clean the mating surfaces on the cylinder head and downpipe thoroughly to ensure a proper seal with the new gaskets. Remove any carbon buildup or old gasket material.
5.3. Installation of New Manifold
- Place the new manifold-to-cylinder head gasket onto the cylinder head studs (if applicable) or align it with the bolt holes.
- Position the new Dorman exhaust manifold onto the cylinder head.
- Install the manifold-to-cylinder head bolts. Hand-tighten them initially.
- Install the new manifold-to-downpipe gasket and connect the downpipe to the manifold using the provided new hardware. Hand-tighten.
- Following your vehicle's service manual, tighten the manifold-to-cylinder head bolts to the specified torque in the correct sequence.
- Tighten the manifold-to-downpipe hardware to the specified torque.
- Reconnect any oxygen sensors or other components that were disconnected.
- Lower the vehicle.
- Reconnect the negative battery terminal.
- Start the engine and check for any exhaust leaks. Listen for unusual noises.
Watch: Make Dorman your exhaust manifold repair solution
Video: An overview of Dorman's exhaust manifold repair solutions, demonstrating the quality and completeness of their kits.
Watch: Why Choose Dorman's Exhaust Manifolds?
Video: Learn about the benefits of choosing Dorman exhaust manifolds, including their engineering, compliance, and warranty.
6. Operating Principles
The exhaust manifold is a critical component of your vehicle's exhaust system. Its primary function is to collect exhaust gases from multiple cylinders and direct them into a single pipe, leading to the catalytic converter and then out through the muffler. This process is essential for efficient engine operation and emissions control. A properly functioning exhaust manifold ensures optimal gas flow, reduces back pressure, and minimizes exhaust leaks, which can affect engine performance and fuel economy.
7. Maintenance
While exhaust manifolds are designed for durability, regular inspection can help identify potential issues early:
- Visual Inspection: Periodically inspect the manifold for visible cracks, rust, or signs of exhaust leaks (e.g., black soot around joints or flanges).
- Listen for Leaks: A ticking or tapping sound, especially when the engine is cold, can indicate an exhaust leak.
- Check Fasteners: Ensure all bolts and nuts securing the manifold and downpipe are tight. Over time, heat cycles can cause them to loosen.
- Emissions System Check: If your vehicle has an integrated catalytic converter, ensure it is functioning correctly as part of your regular emissions checks.
8. Troubleshooting
Common issues related to exhaust manifolds and their potential solutions:
| Symptom | Possible Cause | Solution |
|---|---|---|
| Loud ticking/tapping noise from engine bay (especially when cold) | Exhaust manifold leak (cracked manifold or failed gasket) | Inspect manifold and gaskets. Replace manifold or gaskets as needed. |
| Reduced engine performance or fuel economy | Significant exhaust leak or restricted manifold/catalytic converter | Inspect for leaks or blockages. Replace manifold/converter if damaged. |
| Exhaust smell in cabin | Exhaust leak near the firewall or cabin air intake | Locate and repair the exhaust leak immediately. |
| Check Engine Light (CEL) illuminated | Oxygen sensor issues, catalytic converter inefficiency, or exhaust leak affecting sensor readings | Scan for diagnostic trouble codes (DTCs). Address underlying issue (e.g., replace O2 sensor, manifold/converter, or repair leak). |
9. Specifications
| Attribute | Value |
|---|---|
| Brand | Dorman |
| Model Number | 674-391 |
| Item Weight | 20 pounds |
| Product Dimensions (L x W x H) | 23.88 x 9.63 x 6.63 inches |
| Automotive Fit Type | Vehicle Specific Fit |
| OEM Part Number Equivalents | 101179; SK674391; 10230859; 12553149 |
| Bolt Pattern (Number of Holes) | 8 |
| Exterior Finish | Machined |
10. Warranty & Support
Dorman is committed to providing high-quality replacement parts. Your Dorman exhaust manifold is backed by the following warranty:
- Conventional Manifolds: Backed by a lifetime warranty against defects.
- Manifold Converters (if applicable): Guaranteed for 5 years or 50,000 miles.
For technical support, warranty claims, or further assistance, please visit the official Dorman Products website or contact their customer service directly. Always have your product model number (674-391) and vehicle information ready when seeking support.
Visit DormanProducts.com for more information and to find the correct application for your vehicle.
