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Engine Exhaust System Chevrolet Cobalt I

Exhaust 1 illustration ~2364 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Catalytic Converter Pipe-to-Exhaust Extension Pipe Nuts30 N.m22 lb ft
Catalytic Converter Pipe-to-Exhaust Manifold Nuts50 N.m37 lb ft
Exhaust Heat Shield Retaining Nut10 N.m89 lb in
Exhaust Manifold Heat Shield Bolts25 N.m18 lb ft
Exhaust Manifold-to-Cylinder Head Nuts13 N.m115 lb in
Fuel Tank Strap Bolts25 N.m18 lb ft
Oxygen Sensor42 N.m31 lb ft
Service Exhaust Clamp Nuts45 N.m33 lb ft
Wheel Drive Shaft Heat Shield-to-Engine Block Bolt30 N.m22 lb ft
Wheel Drive Shaft Heat Shield-to-Transmission Mount Bracket Bolt10 N.m89 lb in

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»(/chevrolet/cobalt/i-2004-2010/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»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__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»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  2. Poor acceleration Refer to «Restricted Exhaust»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  3. Poor fuel economy Refer to «Restricted Exhaust»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  4. Excessive smoke-diesel Refer to «Restricted Exhaust»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  5. Exhaust hissing noise Refer to «Exhaust Leakage»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__exhaust-leakage) .
  6. Exhaust popping noise Refer to «Exhaust Leakage»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__exhaust-leakage) .
  7. Exhaust rattle noise Refer to «Exhaust Noise»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__exhaust-noise) .
  8. Loud exhaust noise Refer to «Exhaust Noise»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__exhaust-noise) .
  9. Exhaust buzz, groan, hum noise Refer to «Exhaust Noise»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__exhaust-noise) .

Diagnostic Aids

CAUTIONWhile engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.

Test Description

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

  1. 3: 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 SA9127E or the J 35314-A . See «Special Tools»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system__special-tools) . Removing the heated oxygen sensor (HO2S) sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
  2. 4: This step will isolate the catalytic converter from the remainder of the exhaust system.
  3. 7: 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.
StepActionValue(s)YesNo
1Did you verify the customers complaint?Go to Step 2
2Did you review the exhaust symptoms diagnostic information and perform the necessary inspections?Go to Step 3Go to Symptoms - Engine Exhaust
3Remove the heated oxygen sensor (HO2S) that is in front of and closest to the catalytic converter. Refer to Heated Oxygen Sensor Replacement - Position 1 . Install the SA9127E or J 35314-A in place of the HO2S sensor. See Special Tools . Start the engine. Increase and monitor the engine speed at 2,000 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value?14 kPa (2 psi)Go to Step 4Go to Step 7
4Turn the engine off and place the ignition in the lock position. Remove the SA9127E or J 35314-A . See Special Tools . Re-install the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 1 . Remove the post-catalytst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 . Install the SA9127E or J 35314-A in place of the post HO2S sensor. See Special Tools . Start the engine. Increase and monitor the engine speed at 2,000 RPM. Observe the exhaust system back pressure reading on the gage. Does the reading exceed the specified value?14 kPa (2 psi)Go to Step 5Go to Step 6
5Inspect the exhaust system for the following conditions: Damage in the exhaust pipe Debris in the exhaust pipe Muffler or resonator internal failure Two-layer exhaust pipe separation Did you find and correct the condition?Go to Step 7
6Replace the catalytic converter. Refer to Catalytic Converter Replacement (LSJ) . Did you find and correct the condition?Go to Step 7
7Remove the SA9127E or J 35314-A . See Special Tools . Re-install the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 . Clear any codes. Road test the vehicle in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Restricted Exhaust

Exhaust Leakage

ProblemAction
CAUTION: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system. DEFINITION: An exhaust leak may show stains at the area of the leak. The leak may be felt by holding a hand close to the suspected areas or using a smoke pencil. The leak may make a popping or hissing noise.Refer to Symptoms - Engine Exhaust prior to beginning this table.
Misaligned or improperly installed exhaust system componentsAlign and tighten the components to the specifications. Refer to Fastener Tightening Specifications .
Exhaust leaks at the following connections: Exhaust manifold to pipe Flanges Pipe clampsTighten the components to the specifications. Refer to Fastener Tightening Specifications .
Seals or gaskets leaking. Exhaust manifold to cylinder head Exhaust pipes to exhaust manifold Catalytic converter connection EGR connections AIR connections to the exhaust manifold or cylinder headReplace the leaking seal or gasket. Refer to the affected components procedure for service.
Irregularities at the mating surfaces on the flange connectionsRepair as required or replace the affected component. Refer to the affected components procedure for service.
Exhaust manifold cracked or brokenReplace the exhaust manifold. Refer to Exhaust Manifold Replacement (L61) .
Exhaust system component connection welds leakingReplace the leaking component. Refer to the affected component's procedure for service.
Muffler or resonator, if equipped, damaged or leaking at the seamsReplace the affected muffler. Refer to Muffler Replacement .
CAUTION
While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.

Exhaust Leakage

Exhaust Noise

ConditionAction
CAUTION: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system. DEFINITION: An audible or physical noise due to a faulty component or damaged components causing a loose or misaligned exhaust system resulting in a rattle or vibration noise, i.e. buzz, groan, hum.Refer to Symptoms - Engine Exhaust prior to beginning this table.
Popping or hissing noiseExhaust leak. Refer to Exhaust Leakage .
Loud exhaustCompare to a known good vehicle. Inspect for a damaged or failed muffler. Replace the faulty muffler. Refer to Muffler Replacement .
External rattle or vibration noiseInspect for a bent or loose hanger, loose heat shield, or loose clamp. Inspect for an exhaust pipe causing interference. Repair or replace the affected component. Refer to the affected component's service procedure.
Internal rattleTest the components by tapping with a rubber mallet to confirm a rattle. Replace the faulty catalytic converter, or muffler. Refer to one of the following procedures: Catalytic Converter Replacement (LSJ) Muffler Replacement
CAUTION
While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.

Exhaust Noise

Removal Procedure

  1. Remove the exhaust manifold heat shield.
  2. Remove the oxygen sensor. Refer to «Heated Oxygen Sensor Replacement - Position 1»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-22l-introduction) in Engine Controls - 2.2L (L61).
  3. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  4. Remove the pipe to manifold nuts.
  5. Pull down and back on the exhaust pipe in order to disengage the pipe from the exhaust manifold.
  6. Lower the vehicle.
  7. Remove the exhaust manifold to cylinder head nuts.
  8. Remove the exhaust manifold.
  9. Clean all the sealing surfaces.

Installation Procedure

  1. Install a new exhaust manifold gasket.
  2. Install the exhaust manifold to the cylinder head.
  3. Install the new exhaust manifold to cylinder head retaining nuts. Follow the tightening sequence. Tighten: Tighten the nuts to 13 N.m (115 lb in).
  4. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  5. Install a new exhaust manifold to flex coupler gasket.
  6. Push the flex coupler into position on the exhaust manifold.
  7. Install the retaining nuts which secure the manifold to the flex decoupler. Tighten: Tighten the nuts to 50 N.m (37 lb ft).
  8. Lower the vehicle.
  9. Install the oxygen sensor. Refer to «Heated Oxygen Sensor Replacement - Position 1»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-22l-introduction) in Engine Controls - 2.2L (L61).
  10. Install the exhaust manifold heat shield. Tighten: Tighten the bolts to 25 N.m (18 lb ft).

Note. Do not over-flex or damage the flex decoupler joint when moving the flex decoupler joint from the normal mounting position. The flex decoupler joint will flex a maximum of six degrees which is equivalent to the pipes connected at the joint which move 1 inch for each foot length of pipe. A three foot pipe would move a maximum of three inches.

IMPORTANTA service exhaust muffler will be needed when replacing the exhaust extension pipe on an originally equipped, welded system.
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Support the exhaust muffler.
  3. Cut the exhaust extension pipe just forward of the weld at the front of the exhaust muffler.
  4. Release the muffler from the underbody hanger insulators and remove the exhaust muffler.
  5. Support the catalytic converter pipe.
  6. Remove the catalytic converter pipe-to-exhaust extension pipe nuts.
  7. Release the exhaust extension pipe from the underbody hanger insulators, and support the extension pipe.
  8. Separate the extension pipe from the converter pipe and remove the extension pipe from the vehicle.
  9. Clean the converter pipe flange surface of any remaining gasket material.
  1. Install a NEW exhaust gasket to the service exhaust extension pipe. The gasket is designed to be retained to the flange by the flange studs. Connect the extension pipe to the converter pipe, and support the extension pipe.
  2. Install the catalytic converter pipe-to-exhaust extension pipe nuts. Tighten: Tighten the nuts to 30 N.m (22 lb ft).
  3. Install the exhaust extension pipe to the underbody hangers insulators.
  4. Install the muffler to the vehicle.
  5. Slide the muffler inlet pipe over the extension pipe, then install the muffler insulator to the underbody hanger.
  6. Install a muffler clamp to the muffler inlet pipe. Position the clamp approximately 19 mm (3/4 in) from the edge of the muffler inlet, with the clamp nuts oriented away from the evaporative emission (EVAP) canister.
  7. Align the muffler and tailpipe to the vehicle underbody and rear bumper fascia.
  8. While maintaining muffler positioning, tighten the exhaust clamp nuts. Tighten: Tighten the nuts to 45 N.m (33 lb ft).
  9. Lower the vehicle.
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the post catalytic converter heated oxygen sensor (HO2S). Refer to «Heated Oxygen Sensor Replacement - Position 2»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-20l-introduction) in Engine Controls - 2.0L (LSJ).
  3. Remove the catalytic converter pipe-to-exhaust manifold nuts.
  4. Carefully separate the converter pipe from the exhaust manifold.
  5. Lower the converter pipe to rest on the rear crossmember of the front suspension frame.
  6. Remove the catalytic converter pipe-to-exhaust extension pipe nuts.
  7. Position the converter pipe forward and support the pipe.
  8. Move the extension pipe rearward and down in order to separate the pipes.
  9. Remove the catalytic converter pipe assembly from the vehicle.
  10. If the exhaust gaskets have remained on the vehicle, remove the gaskets from the exhaust manifold and from the exhaust extension pipe, and discard the gaskets.
  11. Clean the flange surfaces of any remaining gasket material.
  1. Install NEW exhaust gaskets to the exhaust manifold and to the exhaust extension pipe. The gaskets are designed to be retained to the flange by the flange studs.
  2. Position the catalytic converter pipe assembly to the vehicle.
  3. Move the extension pipe rearward and down in order to connect the converter pipe to the extension pipe.
  4. Install the catalytic converter pipe-to-exhaust extension pipe nuts. Tighten: Tighten the nuts to 30 N.m (22 lb ft).
  5. Carefully install the converter pipe to the exhaust manifold.
  6. Install the catalytic converter pipe-to-exhaust manifold nuts. Tighten: Tighten the nuts to 50 N.m (37 lb ft).
  7. Install the post catalytic converter HO2S. Refer to «Heated Oxygen Sensor Replacement - Position 2»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-20l-introduction) in Engine Controls - 2.0L (LSJ).
  8. Lower the vehicle.
IMPORTANTThe originally equipped, welded exhaust extension pipe can be cut and reused when installing a service muffler, if the extension pipe is in acceptable condition.
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Support the exhaust muffler.
  3. Cut the exhaust extension pipe just forward of the weld at the front of the exhaust muffler.
  4. Release the muffler from the underbody hanger insulators and remove the exhaust muffler.
  5. Deburr the extension pipe end, as necessary.
  1. Install the muffler to the vehicle.
  2. Slide the muffler inlet pipe over the extension pipe, then install the muffler to the underbody hanger insulators.
  3. Install a muffler clamp to the muffler inlet pipe. Position the clamp approximately 19 mm (3/4 in) from the edge of the muffler inlet, with the clamp nuts oriented away from the evaporative emission (EVAP) canister.
  4. Align the muffler and tailpipe to the vehicle underbody and rear bumper fascia.
  5. While maintaining muffler positioning, tighten the exhaust clamp nuts. Tighten: Tighten the nuts to 45 N.m (33 lb ft).
  6. Lower the vehicle.

Note. Do not over-flex or damage the flex decoupler joint when moving the flex decoupler joint from the normal mounting position. The flex decoupler joint will flex a maximum of six degrees which is equivalent to the pipes connected at the joint which move 1 inch for each foot length of pipe. A three foot pipe would move a maximum of three inches.

  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Separate the post catalytic converter HO2S wiring (1) from the exhaust heat shield.
  3. Remove the catalytic converter pipe from the vehicle, to access the center rivet on the exhaust heat shield. Refer to «Catalytic Converter Replacement (LSJ)»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  4. Release the exhaust extension pipe forward insulators from the underbody hangers, and support the extension pipe.
  5. Remove the exhaust heat shield retaining nut.
  6. Drill out and remove the heat shield retaining rivets.
  7. Remove the heat shield from the vehicle.
  1. Install the exhaust heat shield into position on the vehicle.
  2. Install new heat shield retaining rivets.
  3. Install the exhaust heat shield retaining nut. Tighten: Tighten the nut to 10 N.m (89 lb in).
  4. Remove the support from the exhaust extension pipe.
  5. Install the exhaust extension pipe forward insulators to the underbody hangers.
  6. Install the catalytic converter pipe to the vehicle. Refer to «Catalytic Converter Replacement (LSJ)»(/chevrolet/cobalt/i-2004-2010/remont/exhaust/#engine-exhaust-system) .
  7. Install the post catalytic converter HO2S wiring (1).
  8. Lower the vehicle.
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the wheel drive shaft heat shield-to-transmission mount bracket bolt.
  3. Remove the drive shaft heat shield-to-engine block bolt.
  4. Remove the wheel drive shaft heat shield.
  1. Install the wheel drive shaft heat shield into position on the vehicle.
  2. Install the wheel drive shaft heat shield-to-engine block bolt. Tighten: Tighten the bolt to 30 N.m (22 lb ft).
  3. Install the wheel drive shaft heat shield-to-transmission mount bracket bolt. Tighten: Tighten the bolt to 10 N.m (89 lb in).
  4. Lower the vehicle.
  1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/cobalt/i-2004-2010/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Release the exhaust extension pipe insulators (1, 2) from the underbody hangers.
  3. Release the muffler insulator (3) from the underbody hanger and slowly lower the exhaust to rest on the rear axle beam.
  4. Support the LH side of the fuel tank, just clear of the fuel tank heat shield.
  5. Remove the LH fuel tank strap bolts and the strap.
  6. Using a flat-bladed screwdriver, release the heat shield push-rivet style retainers (1).
  7. Remove the fuel tank heat shield from the vehicle.
  1. Carefully install the fuel tank heat shield into position on the fuel tank.
  2. Install the heat shield retainers into position, then press to secure the retainers. Ensure that each of the retainers is fully seated.
  3. Install the LH fuel tank strap and strap bolts.
  4. Tighten the fuel tank strap bolts. Tighten: Tighten the bolts to 25 N.m (18 lb ft).
  5. Remove the support from the fuel tank.
  6. Raise the exhaust into position and install the muffler insulator (3) to the underbody hanger.
  7. Install the exhaust extension pipe insulators (1, 2) to the underbody hangers.
  8. Lower the vehicle.

Exhaust System Description

IMPORTANTUse of non-OEM parts may cause driveability concerns.

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 tailpipe, 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.

Special Tools

Special Tools Illustration Tool Number/Description J 35314-A Exhaust Back Pressure Gage

Scheme 1

Scheme 1: Special Tools
Scheme 1: Special Tools