Maintaining an intact and leak-free exhaust system is crucial for optimal engine performance, fuel efficiency, and emissions control in the fourth-generation Honda Prelude (BB chassis). Over time, components such as the mid-pipe, muffler, and downpipe can corrode or fail, leading to exhaust leaks and increased noise. This guide outlines the general procedure for replacing exhaust components and performing a comprehensive leak test.

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Exhaust System Overview#

The exhaust system on the fourth-generation Prelude typically consists of a downpipe (often referred to as 'headers' or 'штаны' in some contexts), a catalytic converter, a mid-pipe (resonator section), and a muffler. Some aftermarket or previously modified systems may feature welded sections, making individual component replacement more challenging.

Important

Always consult the factory service manual (FSM) for your specific model year and engine variant (e.g., H22, F22) to confirm exact component configurations, torque specifications, and specialized procedures.

Tools and Materials#

Before beginning, gather the necessary tools and replacement parts:

• Replacement Exhaust Components: Downpipe, catalytic converter, mid-pipe/resonator, muffler, gaskets, and exhaust clamps as needed.
• Hand Tools: Ratchets, sockets, wrenches (including oxygen sensor wrench if applicable).
• Cutting Tools: Sawzall or exhaust pipe cutter (if sections need to be cut).
• Cleaning Supplies: Wire brush, sandpaper, rust penetrant.
• Sealant: High-temperature exhaust system sealant-cement (e.g., ceramic-based, rated up to 1100°C).
• Safety Gear: Safety glasses, gloves, jack stands.
• Diagnostic Tool: Smoke generator for leak detection (e.g., Autool C4 or similar).
• Fire Extinguisher: Always have one readily available when working with fuel or exhaust systems.

Exhaust Component Replacement Procedure#

Replacing exhaust components typically involves several key steps:

1. Vehicle Preparation and Safety#

1. Park the vehicle on a level surface.
2. Engage the parking brake and block the wheels.
3. Safely lift the vehicle using a jack and secure it with jack stands.
4. Allow the exhaust system to cool completely before working on it.

Warning

Never work under a vehicle supported only by a jack. Always use sturdy jack stands.

2. Exhaust System Inspection#

Thoroughly inspect the existing exhaust system for:

• Corrosion: Rust on pipes, flanges, and hangers.
• Cracks or Holes: Especially common on mid-pipes and mufflers.
• Loose Connections: Check bolts, clamps, and hangers.
• Previous Repairs: Note any welded sections that might complicate removal.

3. Component Removal#

1. Apply rust penetrant to all bolts and nuts connecting exhaust sections and hangers. Allow it to soak.
2. Disconnect any oxygen sensors if they are located in the section being removed. Be careful not to damage the wiring.
3. Starting from the rear, unbolt and detach the muffler from its hangers and the mid-pipe.
4. Proceed to the mid-pipe, unbolting it from the catalytic converter or downpipe and releasing it from its hangers.
5. If replacing the downpipe or catalytic converter, unbolt them from the exhaust manifold and any supporting brackets.

Tip

If bolts are severely rusted, a cutting tool may be necessary. Exercise caution to avoid damaging surrounding components.

4. Installation of New Components#

1. Clean all mating surfaces on the remaining exhaust components and the new parts. Remove old gasket material, rust, and dirt.
2. Install new gaskets between flanges. Use a thin layer of high-temperature exhaust sealant-cement on mating surfaces as directed by the product instructions.
3. Begin installing new components from the front (downpipe/catalytic converter) towards the rear (muffler).
4. Hand-tighten all bolts and clamps first to allow for adjustment and alignment.
5. Ensure all components are properly aligned and clear of the chassis, suspension, and fuel lines.
6. Once aligned, progressively tighten all bolts and clamps to the manufacturer's specified torque values. Refer to the FSM.
7. Reconnect any oxygen sensors.

Exhaust Sealant Application#

For ceramic high-temperature exhaust sealant-cement, follow these general steps:

• Clean Surface: Ensure the application area is free of dirt, rust, and grease.
• Apply Sealant: Apply an even layer to the damaged area or mating surfaces.
• Initial Hardening: Start the engine for 15-20 minutes to initiate hardening from heat exposure.
• Full Cure: Allow 24 hours for full hardening. Repeat if necessary.

5. Post-Installation Checks#

1. Double-check all connections for tightness.
2. Ensure adequate clearance around all exhaust components.
3. Lower the vehicle from the jack stands.

Exhaust System Leak Testing#

After replacement, it is critical to test the entire exhaust system for leaks. A smoke generator is an effective tool for this.

1. Preparation for Smoke Test#

1. Ensure the engine is off and cool.
2. Block off the exhaust tip(s) securely using a plug or a rag and tape to prevent smoke from escaping.
3. Connect the smoke generator's output hose to an accessible point in the exhaust system, such as an oxygen sensor bung or directly into the exhaust pipe near the front.
4. Connect the smoke generator to a 12V power source (e.g., the vehicle's battery).

2. Performing the Smoke Test#

1. Turn on the smoke generator. Allow it to build pressure and introduce smoke into the exhaust system.
2. Carefully inspect the entire exhaust system, from the manifold to the muffler, for any visible smoke escaping.
3. Pay close attention to:
   • Flange connections and gaskets.
   • Welds and seams.
   • Exhaust clamps.
   • Any areas where previous repairs were made.
   • The body of the muffler and resonator.

Important

A comprehensive smoke test can reveal leaks beyond the exhaust system. For example, a smoke test on a fourth-generation Prelude once revealed an air intake leak at the Intake Air Bypass (IAB) valve shaft, indicating a separate issue that could affect engine performance.

3. Addressing Leaks#

• Minor Leaks: Small leaks at flanges or clamps may be resolved by tightening fasteners or applying additional high-temperature exhaust sealant.
• Major Leaks: Larger leaks, cracks, or holes may require re-welding, replacing the affected component, or using specialized exhaust repair bandages.

Caution

Never run the engine with a smoke generator connected to the intake system unless specifically instructed by the diagnostic tool's manufacturer, as some smoke fluids can damage sensitive engine components.

By following these procedures, you can effectively replace your fourth-generation Honda Prelude's exhaust system and ensure it is free of performance-robbing leaks. Always consult the factory service manual for specific torque values and detailed diagrams relevant to your vehicle's exact configuration.