Engine Exhaust System Buick Century VI

Fastener Tightening Specifications

Fastener Tightening Specifications

Diagnostic Starting Point - Engine Exhaust

Begin the system diagnosis by reviewing the system Description and Operation. Reviewing the information will help you determine the correct symptom diagnostic procedure when a malfunction exists. It will also help you determine if the condition described by the customer is normal operation. Refer to SYMPTOMS - ENGINE EXHAUST in order to identify the correct procedure for diagnosing the system.

Symptoms - Engine Exhaust

1. Review the Exhaust System Description and Operation in order to familiarize yourself with the system functions. Refer to «EXHAUST SYSTEM DESCRIPTION»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system__exhaust-system-description) .
2. All diagnostics on a vehicle should follow a logical process. Strategy Based Diagnostics is a uniform approach for repairing all systems. The diagnostic flow is the place to start when repairs are necessary and may always be used in order to resolve a system problem. For a detailed explanation, refer to Strategy Based Diagnosis in General Information.

Visual/Physical Inspection

1. Inspect for aftermarket or non-OEM devices such as, but not including; tailpipe extensions, headers, and exhaust cutouts. This could affect the operation and proper performance of the exhaust system.
2. Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, engine temperature, engine load, and frequency of concern.
3. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause any symptom.

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system is operating as designed.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. Loss of Power Refer to «RESTRICTED EXHAUST»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
2. Poor acceleration Refer to «RESTRICTED EXHAUST»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
3. Poor fuel economy Refer to «RESTRICTED EXHAUST»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
4. Excessive smoke-diesel Refer to «RESTRICTED EXHAUST»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
5. Exhaust hissing noise Refer to «EXHAUST LEAKAGE»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
6. Exhaust popping noise Refer to «EXHAUST LEAKAGE»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
7. Exhaust rattle noise Refer to «EXHAUST NOISE»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
8. Loud exhaust noise Refer to «EXHAUST NOISE»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
9. Exhaust buzz, groan, hum noise Refer to «EXHAUST NOISE»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .

Diagnostic Aids

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and the diagnosis should begin there.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 4. The exhaust system has very low back pressure under normal conditions. If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the J 35314-A Exhaust Back Pressure Gage. Removing the HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
2. 5. This step will isolate the catalytic converter from the remainder of the exhaust system.
3. 8. Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to Step 2 and repeat diagnostic procedure on the opposite exhaust pipe.
4. 9. Confirming that the condition has been fixed is essential. If the symptom still exists, proceed to Step 2 and repeat the diagnostic procedure.

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1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.
2. Remove the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
3. Remove the right engine mount strut bracket. Refer to ENGINE MOUNT STRUT BRACKET REPLACEMENT - RIGHT in Engine Mechanical - 3.1L.
4. Remove the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
5. Remove the exhaust crossover pipe heat shield bolts.
6. Remove the exhaust crossover pipe heat shield.
7. Remove the exhaust crossover pipe nuts from the left exhaust manifold.
8. Remove the left exhaust manifold heat shield bolts.
9. Remove the left exhaust manifold heat shield.
10. Remove the left exhaust manifold nuts.
11. Remove the left exhaust manifold.
12. Remove the left exhaust manifold gasket.
13. Clean and inspect the left exhaust manifold. Refer to EXHAUST MANIFOLD CLEANING AND INSPECTION in Engine Mechanical - 3.1L.

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1. Install the left exhaust manifold gasket.
2. Install the left exhaust manifold. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
3. Install the left exhaust manifold nuts. Tighten Tighten the nuts to 16 N.m (12 lb ft).
4. Install the left exhaust manifold heat shield.
5. Install the left exhaust manifold heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
6. Install the exhaust crossover pipe nuts to the left exhaust manifold. Tighten Tighten the nuts to 25 N.m (18 lb ft).
7. Install the exhaust crossover pipe heat shield.
8. Install the exhaust crossover pipe heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
9. Install the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
10. Install the right engine mount strut bracket. Refer to ENGINE MOUNT STRUT BRACKET REPLACEMENT - RIGHT in Engine Mechanical - 3.1L.
11. Install the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
12. Connect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.

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1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.
2. Remove the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8L.
3. Remove the engine mount struts. Refer to ENGINE MOUNT STRUT REPLACEMENT - RIGHT and ENGINE MOUNT STRUT REPLACEMENT - LEFT in Engine Mechanical - 3.8L.
4. Remove the lower right engine mount strut bracket. Refer to ENGINE MOUNT STRUT BRACKET REPLACEMENT - RIGHT LOWER in Engine Mechanical - 3.8L.
5. Remove the exhaust crossover pipe bolts from the left exhaust manifold.
6. Remove the left spark plugs from cylinders 1, 3 and 5. Refer to «SPARK PLUGS»(ref-159248-S28146450102003112000000) in Self-Diagnostics - 3.8L.
7. Remove the oil level indicator tube. Refer to OIL LEVEL INDICATOR AND TUBE REPLACEMENT in Engine Mechanical - 3.8L.
8. Remove the left engine lift bracket bolt and the nut.
9. Remove the left engine lift bracket
10. Remove the exhaust manifold heat shield nuts.
11. Remove the exhaust manifold heat shield.
12. Remove the exhaust manifold bolts and the nuts.
13. Remove the exhaust manifold.
14. Remove the exhaust manifold gasket.
15. Clean and inspect the left exhaust manifold. Refer to EXHAUST MANIFOLD CLEANING AND INSPECTION in Engine Mechanical - 3.8L.

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1. Install the new exhaust manifold gasket.
2. Install the exhaust manifold. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
3. Install the exhaust manifold bolts and the nuts. Tighten Tighten the bolts and the nuts to 30 N.m (22 lb ft).
4. Install the exhaust manifold heat shield.
5. Install the exhaust manifold heat shield nuts. Tighten Tighten the nuts to 20 N.m (15 lb ft).
6. Install the engine lift bracket.
7. Install the engine lift bracket bolt and the nut. Tighten Tighten the bolt and the nut to 30 N.m (22 lb ft).
8. Install the oil level indicator tube. Refer to OIL LEVEL INDICATOR AND TUBE REPLACEMENT in Engine Mechanical - 3.8L.
9. Install the left spark plugs to cylinders 1, 3 and 5. Refer to «SPARK PLUGS»(ref-159248-S28146450102003112000000) in Self-Diagnostics - 3.8L.
10. Install the exhaust crossover bolts to the left exhaust manifold. Tighten Tighten the bolts to 20 N.m (15 lb ft).
11. Install the lower right engine mount strut bracket. Refer to ENGINE MOUNT STRUT BRACKET REPLACEMENT - RIGHT LOWER in Engine Mechanical - 3.8L.
12. Install the engine mount struts. Refer to ENGINE MOUNT STRUT REPLACEMENT - RIGHT and ENGINE MOUNT STRUT REPLACEMENT - LEFT in Engine Mechanical - 3.8L.
13. Install the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8L.
14. Connect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.

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1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.
2. Remove the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
3. Remove the accelerator and cruise control cables with the bracket from the throttle body.
4. Rotate the engine for service access. Refer to ROTATING THE ENGINE FOR SERVICE ACCESS in Engine Mechanical - 3.1L.
5. Remove the manifold absolute pressure (MAP) sensor. Refer to «MANIFOLD ABSOLUTE PRESSURE SENSOR»(ref-159248-S40793749462003112000000) in Removal & Installation.
6. Remove the ignition control module and the ignition control module bracket. Refer to «IGNITION CONTROL MODULE»(ref-159248-S13093826002003112000000)
7. Disconnect the heated oxygen (HO2S) sensor electrical connector.
8. Remove the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
9. Remove the exhaust crossover pipe heat shield bolts.
10. Remove the exhaust crossover pipe heat shield.
11. Remove the exhaust crossover pipe nuts from the right exhaust manifold.
12. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
13. Remove the catalytic converter. Refer to «CATALYTIC CONVERTER REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) or «CATALYTIC CONVERTER REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
14. Remove the exhaust gas recirculation (EGR) pipe from the right exhaust manifold. Refer to «EGR VALVE PIPE»(ref-159248-S25017201312003112000000)
15. Remove the right exhaust manifold upper heat shield bolts.
16. Remove the right exhaust manifold upper heat shield.
17. Remove the right exhaust manifold lower heat shield bolts.
18. Remove the right exhaust manifold lower heat shield.
19. Remove the right exhaust manifold nuts.
20. Remove the right exhaust manifold.
21. Remove the right exhaust manifold gasket.
22. Clean and inspect the right exhaust manifold. Refer to EXHAUST MANIFOLD CLEANING AND INSPECTION in Engine Mechanical - 3.1L.
23. If replacing the right exhaust manifold remove the heated oxygen (HO2S) sensor. Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.

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1. If replacing the right exhaust manifold install the heated oxygen (HO2S) sensor. Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.
2. Install the right exhaust manifold gasket.
3. Install the right exhaust manifold. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Install the right exhaust manifold nuts. Tighten Tighten the nuts to 16 N.m (12 lb ft).
5. Install the right exhaust manifold lower heat shield.
6. Install the right exhaust manifold lower heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
7. Install the right exhaust manifold upper heat shield.
8. Install the right exhaust manifold upper heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
9. Install the EGR pipe to the right exhaust manifold. Refer to «EGR VALVE PIPE»(ref-159248-S25017201312003112000000)
10. Install the catalytic converter. Refer to «CATALYTIC CONVERTER REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) or «CATALYTIC CONVERTER REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
11. Lower the vehicle.
12. Install the exhaust crossover pipe nuts to the right exhaust manifold. Tighten Tighten the nuts to 25 N.m (18 lb ft).
13. Install the exhaust crossover pipe heat shield.
14. Install the exhaust crossover pipe heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
15. Install the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
16. Connect the heated oxygen (HO2S) sensor electrical connector.
17. Install the ignition control module and the ignition control module bracket. Refer to «IGNITION CONTROL MODULE»(ref-159248-S13093826002003112000000)
18. Install the MAP sensor. Refer to «MANIFOLD ABSOLUTE PRESSURE SENSOR»(ref-159248-S40793749462003112000000) in Removal & Installation.
19. Return the engine to the original position.
20. Install the engine mount struts. Refer to ENGINE MOUNT STRUT REPLACEMENT in Engine Mechanical - 3.1L.
21. Install the accelerator and cruise control cables with the bracket to the throttle body.
22. Install the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
23. Connect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Battery.

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1. Remove the cross vehicle brace. Refer to BRACE REPLACEMENT - CROSS VEHICLE in Body Front End.
2. Remove the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8L.
3. Remove the exhaust crossover heat shield nuts.
4. Remove the exhaust crossover heat shield.
5. Remove the exhaust crossover pipe bolts from the right exhaust manifold.
6. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
7. Remove the exhaust manifold pipe stud nuts and the catalytic converter pipe from the right exhaust manifold.
8. Remove the exhaust gas recirculation (EGR) valve inlet adapter pipe bolt from the right exhaust manifold.
9. Lower the vehicle.
10. Rotate the engine to access the right side of the engine. Refer to ROTATING THE ENGINE FOR SERVICE ACCESS in Engine Mechanical - 3.8L.
11. Disconnect the heated oxygen (HO2S) sensor electrical connector (4).
12. Remove the heated oxygen (HO2S) sensor electrical connector (4) from the engine sight shield bracket (1).
13. Remove the right side spark plugs from cylinders 2, 4 and 6. Refer to «SPARK PLUGS»(ref-159248-S28146450102003112000000) in Self-Diagnostics - 3.8L.
14. Remove the right engine lift bracket bolt and the nut.
15. Remove the right engine lift bracket.
16. Remove the fuel injector sight shield bracket nuts.
17. Remove the fuel injector sight shield bracket.
18. Remove the right exhaust manifold bolts and the nuts.
19. Remove the right exhaust manifold.
20. Remove the right exhaust manifold gasket.
21. Remove the upper right exhaust manifold heat shield.
22. Remove the lower right exhaust manifold heat shield.
23. If replacing the right exhaust manifold remove the heated oxygen (HO2S) sensor from the right exhaust manifold. Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.
24. Remove the exhaust manifold studs if damaged.
25. Clean and Inspect the right exhaust manifold. Refer to EXHAUST MANIFOLD CLEANING AND INSPECTION in Engine Mechanical - 3.8L.

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1. Install the exhaust manifold studs if removed.
2. If replacing the right exhaust manifold, install the heated oxygen (HO2S) sensor to the right exhaust manifold. Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.
3. Install the lower right exhaust manifold heat shield.
4. Install the upper right exhaust manifold heat shield.
5. Install the new right exhaust manifold gasket.
6. Install the right exhaust manifold. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
7. Install the right exhaust manifold bolts and the nuts. Tighten Tighten the bolts and the nuts to 30 N.m (22 lb ft).
8. Install the fuel injector sight shield bracket.
9. Install the fuel injector sight shield bracket nuts. Tighten Tighten the nuts to 30 N.m (22 lb ft).
10. Install the right engine lift bracket.
11. Install the right engine lift bracket bolt and the nut. Tighten Tighten the bolt and the nut to 30 N.m (22 lb ft).
12. Install the right side spark plugs to cylinders 2, 4 and 6. Refer to «SPARK PLUGS»(ref-159248-S28146450102003112000000) in Self-Diagnostics - 3.8L.
13. Install the heated oxygen (HO2S) sensor electrical connector (4) to the engine sight shield bracket (1).
14. Connect the heated oxygen (HO2S) sensor electrical connector (4).
15. Return the engine to the original position.
16. Raise the vehicle.
17. Install the EGR valve inlet adapter pipe to the right exhaust manifold. Tighten Tighten the bolt to 29 N.m (21 lb ft).
18. Install the catalytic converter pipe to the right exhaust manifold.
19. Install the catalytic converter pipe stud nuts to the right exhaust manifold. Tighten Tighten the stud nuts to 35 N.m (26 lb ft).
20. Lower the vehicle.
21. Install the exhaust crossover bolts to the right exhaust manifold. Tighten Tighten the bolts to 20 N.m (15 lb ft).
22. Install the exhaust crossover heat shield.
23. Install the exhaust crossover heat shield nuts. Tighten Tighten the nuts to 20 N.m (15 lb ft).
24. Install the engine mount struts. Refer to ENGINE MOUNT STRUT REPLACEMENT - RIGHT and ENGINE MOUNT STRUT REPLACEMENT - LEFT in Engine Mechanical - 3.8L.
25. Install the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8L.
26. Install the cross vehicle brace. Refer to BRACE REPLACEMENT - CROSS VEHICLE in Body Front End.

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1. Remove the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
2. Remove the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
3. Remove the exhaust crossover heat shield bolts.
4. Remove the exhaust crossover heat shield.
5. Remove the exhaust crossover pipe nuts.
6. Remove the exhaust crossover pipe.

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1. Install the exhaust crossover pipe. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the exhaust crossover pipe nuts. Tighten Tighten the nuts to 25 N.m (18 lb ft).
3. Install the exhaust crossover heat shield.
4. Install the exhaust crossover heat shield bolts. Tighten Tighten the bolts to 10 N.m (89 lb in).
5. Install the thermostat bypass pipe. Refer to THERMOSTAT BYPASS PIPES REPLACEMENT in Engine Cooling.
6. Install the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.

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1. Remove the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8
2. Remove the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
3. Remove the exhaust crossover heat shield nuts.
4. Remove the exhaust crossover heat shield.
5. Remove the exhaust crossover pipe bolts.
6. Remove the exhaust crossover pipe.
7. Remove the exhaust crossover pipe seal.

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1. Install the exhaust crossover pipe seal to the exhaust crossover pipe at the right exhaust manifold connection.
2. Install the exhaust crossover pipe. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
3. Install the exhaust crossover pipe bolts. Tighten Tighten the bolts to 20 N.m (15 lb ft).
4. Install the exhaust crossover heat shield.
5. Install the exhaust crossover heat shield nuts. Tighten Tighten the nuts to 20 N.m (15 lb ft).
6. Install the air cleaner intake duct. Refer to «AIR CLEANER INTAKE DUCT»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) in Removal & Installation - A/T.
7. Install the fuel injector sight shield. Refer to FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L36) or FUEL INJECTOR SIGHT SHIELD REPLACEMENT (L67) in Engine Mechanical - 3.8L.

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1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices. IMPORTANT: Use caution handling the pipe that contains an oxygen sensor. Do not cut the wire. For removal or repositioning disconnect the connector.
2. Remove the exhaust manifold pipe stud nuts from the exhaust manifold studs. IMPORTANT: Support the exhaust system where hangers are removed.
3. Remove the catalytic converter exhaust hangers.
4. Reposition the exhaust system.
5. Remove the exhaust manifold pipe gasket.

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1. Install the exhaust manifold pipe gasket.
2. Install the exhaust system to the original position.
3. Install the catalytic converter exhaust hangers.
4. Remove the support from the exhaust system. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
5. Install the exhaust manifold pipe nuts to the exhaust manifold pipe studs. Tighten Tighten the nuts to 35 N.m (26 lb ft).
6. Inspect the exhaust system for leaks and underbody contact.
7. Lower the vehicle.

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1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices. IMPORTANT: Exercise caution handling the pipe that contains an oxygen sensor. Do not cut the wire. For removal or repositioning disconnect the connector.
2. Remove the exhaust manifold nuts from the exhaust manifold pipe studs. IMPORTANT: Support the exhaust system where hangers are removed.
3. Remove the catalytic converter exhaust hangers.
4. Reposition the exhaust system.
5. Remove the exhaust manifold pipe gasket.

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1. Install the exhaust manifold pipe gasket.
2. Install the exhaust system to the original position
3. Install the catalytic converter exhaust hangers.
4. Remove the support from the exhaust system. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
5. Install the exhaust manifold pipe nuts to the exhaust manifold pipe studs. Tighten Tighten the nuts to 35 N.m (26 lb ft).
6. Inspect the exhaust system for leaks and underbody contact.
7. Lower the vehicle.

Removal Procedure

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1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
2. Disconnect the heated oxygen sensor (HO2S) electrical connector.
3. Remove the exhaust manifold pipe stud nuts.
4. Remove the exhaust manifold pipe gasket.
5. Support the exhaust system.
6. Remove the catalytic converter nuts.
7. Remove the catalytic converter hangers.
8. Remove the 3-way catalytic converter.
9. Remove the catalytic converter gasket.
10. Clean and inspect the exhaust manifold and the exhaust pipe gasket mating surfaces.
11. Remove the heated oxygen sensor (HO2S). Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.

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1. Install the heated oxygen sensor (HO2S). Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation. NOTE: To prevent internal damage to the flexible coupling of the catalytic converter assembly, the converter must be supported. The vertical movement at the rear of the catalytic converter assembly must not exceed 6 degrees up or down.
2. Install a new gasket to the exhaust pipe studs.
3. Install and support the 3-way catalytic converter. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Install the catalytic converter nuts. Tighten Tighten the nuts to 60 N.m (44 lb ft).
5. Install a new exhaust manifold pipe gasket.
6. Install the exhaust manifold pipe stud nuts. Tighten Tighten the nuts to 35 N.m (26 lb ft).
7. Install the catalytic converter hangers.
8. Remove the support from the exhaust system.
9. Connect the heated oxygen sensor (HO2S) electrical connector.
10. Inspect the exhaust system for leaks and underbody contact.
11. Lower the vehicle.

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1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
2. Disconnect the heated oxygen sensor (HO2S) electrical connector.
3. Remove the exhaust manifold pipe stud nuts.
4. Remove the exhaust manifold pipe gasket.
5. Support the exhaust system.
6. Remove the catalytic converter nuts.
7. Remove the catalytic converter hangers.
8. Remove the 3-way catalytic converter.
9. Remove the catalytic converter gasket.
10. Clean and inspect the exhaust manifold and the exhaust pipe gasket mating surfaces.
11. Remove the heated oxygen sensor (HO2S). Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation.

Scheme 85

Scheme 86

Scheme 87

1. Install the heated oxygen sensor (HO2S). Refer to «HEATED OXYGEN SENSOR»(ref-159248-S21108199762003112000000) in Removal & Installation. NOTE: To prevent internal damage to the flexible coupling of the catalytic converter assembly, the converter must be supported. The vertical movement at the rear of the catalytic converter assembly must not exceed 6 degrees up or down.
2. Install a new gasket to the exhaust pipe studs.
3. Install and support the 3-way catalytic converter. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Install the catalytic converter nuts. Tighten Tighten the nuts to 60 N.m (44 lb ft).
5. Install a new exhaust manifold pipe gasket.
6. Install the exhaust manifold pipe stud nuts. Tighten Tighten the nuts to 35 N.m (26 lb ft).
7. Install the catalytic converter hangers.
8. Remove the support from the exhaust system.
9. Connect the heated oxygen sensor (HO2S) electrical connector.
10. Inspect the exhaust system for leaks and underbody contact.
11. Lower the vehicle.

Scheme 88

Scheme 89

Scheme 90

1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information.
2. Support the exhaust system.
3. Remove the exhaust pipe hanger (3) from the exhaust pipe (2) and the exhaust hanger bracket (1).
4. Remove the exhaust pipe hanger from the exhaust pipe and the exhaust hanger bracket.
5. Remove the exhaust pipe rear hangers from the muffler and the rear exhaust hanger brackets.

Scheme 91

Scheme 92

Scheme 93

1. Install the exhaust pipe rear hangers to the muffler and the rear exhaust hanger brackets.
2. Install the exhaust pipe hanger to the exhaust pipe and the exhaust hanger bracket.
3. Install the exhaust pipe hanger (3) to the exhaust pipe (2) and the exhaust hanger bracket (1).
4. Remove the support from the exhaust system.
5. Inspect the exhaust system for underbody contact.
6. Lower the vehicle.

Scheme 94

Scheme 95

1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices.
2. Support the exhaust system.
3. Remove the exhaust pipe rear hanger insulators from the exhaust muffler rear hanger bracket.
4. Loosen the outboard rear bumper impact bar bolt.
5. Remove the inboard rear bumper impact bar bolt.
6. Remove the exhaust muffler rear hanger bracket.

Scheme 96

Scheme 97

1. Install the exhaust muffler rear hanger bracket. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the inboard and the outboard rear bumper impact bar bolts. Tighten Tighten the bolts to 25 N.m (18 lb ft).
3. Install the exhaust pipe rear hanger insulators to the exhaust muffler rear hanger bracket.
4. Remove the support from the exhaust system.
5. Inspect the exhaust system for underbody contact.
6. Lower the vehicle.

Scheme 98

Scheme 99

1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices.
2. Support the exhaust system.
3. Remove the catalytic converter bolts.
4. Remove the catalytic converter gasket.
5. Remove the exhaust hanger insulators from the muffler.
6. Remove the muffler from the support.

Scheme 100

Scheme 101

1. Install the muffler to the support.
2. Install the exhaust hanger insulators to the muffler.
3. Install the catalytic converter gasket. NOTE: Refer to «FASTENER NOTICE»(/buick/century/vi-1997-2005/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Install the catalytic converter bolts. Tighten Tighten the bolts to 45 N.m (33 lb ft).
5. Remove the support from the exhaust system.
6. Inspect the exhaust system for leaks and underbody contact.
7. Lower the vehicle.

Scheme 102

1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices.
2. Support the exhaust system.
3. Remove the 3-way catalytic converter pipe hangers.
4. Inspect the 3-way catalytic converter brackets for serviceability. Repair or replace as necessary.

Scheme 103

1. Install the 3-way catalytic converter pipe hangers.
2. Remove the support from the exhaust system and the vehicle.
3. Inspect the exhaust system for underbody contact.
4. Lower the vehicle.

Scheme 104

Scheme 105

1. Raise and support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(/buick/century/vi-1997-2005/remont/hoistjack/#jacking-and-lifting__lifting-and-jacking-the-vehicle) in General Information. NOTE: Refer to Catalytic Converter Movement Notice in Cautions and Notices.
2. Support the exhaust system.
3. Remove the catalytic converter. Refer to «CATALYTIC CONVERTER REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) or «CATALYTIC CONVERTER REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
4. Remove the oxygen sensor wiring harness (3) from the catalytic converter heat shield.
5. Remove the catalytic converter heat shield rivets.
6. Remove the catalytic converter heat shield.

Scheme 106

Scheme 107

1. Install the catalytic converter heat shield.
2. Install the converter heat shield rivets.
3. Install the oxygen sensor wiring harness (3) to the catalytic converter heat shield.
4. Install the catalytic converter. Refer to «CATALYTIC CONVERTER REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) or «CATALYTIC CONVERTER REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/exhaust/#engine-exhaust-system) .
5. Remove the support from the exhaust system.
6. Inspect the exhaust system for leaks and underbody contact.
7. Lower the vehicle.

Exhaust System Description

The exhaust system carries exhaust gases, treated by the catalytic converter, through a resonator, if applicable and into the exhaust muffler where exhaust noise is lessened.

In order to secure the exhaust pipe to the exhaust manifold, a flange and seal-joint coupling is utilized. The exhaust system may utilize a slip-joint coupling design with a clamp and a U-bolt or a flange connection with a gasket.

Exhaust hangers and rubber insulators help to support the weight of the exhaust pipe along with insulating any exhaust system vibration, rattle, or noise.

Exhaust hangers also space the exhaust system away from the underbody of the vehicle and allows the exhaust system to expand as the exhaust system warms up.

Exhaust heat shields are used to protect the body and other components from damage due to the heat from the exhaust system.

The exhaust system may be comprised of the following components

1. Exhaust manifold
2. Exhaust pipes
3. Catalytic converters
4. Exhaust muffler
5. Exhaust resonator, if equipped
6. Exhaust tail pipe, if equipped
7. Exhaust hangers
8. Exhaust heat shields

Resonator

Some exhaust systems are equipped with a resonator. The resonator, located either before or after the muffler, allows the use of mufflers with less back pressure. Resonators are used when vehicle characteristics require specific exhaust tuning.

Catalytic Converter

The catalytic converter is an emission control device added to the engine exhaust system in order to reduce hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) pollutants from the exhaust gas.

The catalytic converter is comprised of a ceramic monolith substrate, supported in insulation and housed within a sheet metal shell. The substrate may be washcoated with 3 noble metals

1. Platinum (Pt)
2. Palladium (Pd)
3. Rhodium (Rh)

The catalyst in the converter is not serviceable.

Muffler

The exhaust muffler reduces the noise levels of the engine exhaust by the use of tuning tubes. The tuning tubes create channels inside the exhaust muffler that lower the sound levels created by the combustion of the engine.

Scheme 108

See also:
• AIR CLEANER INTAKE DUCT
• FASTENER NOTICE
• LIFTING AND JACKING THE VEHICLE
• SYMPTOMS - ENGINE EXHAUST
• EXHAUST SYSTEM DESCRIPTION
• RESTRICTED EXHAUST