Engine Exhaust System: Overview Chevrolet TrailBlazer I

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 . Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
2. 5. If high back pressure is not found at idle, increasing the engine speed may help find a restriction. Perform operational check before returning vehicle to customer.
3. 6. This step will isolate the catalytic converter from the remainder of the exhaust system.
4. 9. 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.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

1. Remove the air cleaner resonator outlet duct. Refer to «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000) .
2. Remove the transmission filler tube stud nut from the A.I.R. adapter and move filler tube out of the way.
3. Remove the oil level indicator tube. Refer to OIL LEVEL INDICATOR AND TUBE REPLACEMENT .
4. Remove the oxygen sensor from the exhaust manifold. Refer to «OXYGEN SENSORS (4.2L)»(ref-159085-S26001549372003111100000) .
5. Remove 4 manifold heat shield nuts and remove the heat shield.
6. Raise the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(ref-188480-S19457848752005090300000) in General Information.
7. Loosen and remove the exhaust pipe bolts from the exhaust manifold.
8. Lower vehicle.
9. Loosen and remove the exhaust manifold bolts.
10. Remove the exhaust manifold.
11. Remove the exhaust manifold gasket.

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

1. Install a new exhaust manifold gasket.
2. Install the exhaust manifold. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
3. With threadlock GM P/N 12345493 (Canadian P/N 10953488) on the manifold bolts, install the bolts onto the manifold. Tighten 3.1. Tighten the exhaust manifold bolts first pass in sequence to 20 N.m (15 lb ft). 3.2. Tighten the exhaust manifold bolts second pass in sequence to 20 N.m (15 lb ft). 3.3. Tighten the exhaust manifold bolts final pass in sequence to 20 N.m (15 lb ft).
4. Install the exhaust manifold heat shield studs, if required. Tighten Tighten the heat shield studs to 10 N.m (89 lb in).
5. Install the oxygen sensor. Refer to «OXYGEN SENSORS (4.2L)»(ref-159085-S26001549372003111100000) .
6. Install the exhaust manifold heat shield.
7. Add anti-seize compound GM P/N 12371386 to the exhaust manifold heat shield nuts.
8. Install the exhaust manifold heat shield nuts. Tighten Tighten the exhaust manifold heat shield nuts to 5 N.m (44 lb in).
9. Raise the vehicle.
10. Install the exhaust pipe to the manifold with seal and secure the pipe with the nuts. Tighten Tighten the exhaust pipe nuts to 50 N.m (37 lb ft).
11. Lower the vehicle.
12. Install the oil level indicator tube. Refer to OIL LEVEL INDICATOR AND TUBE REPLACEMENT .
13. Move the transmission filler tube back onto the A.I.R. adapter block stud and secure the tube with the nut. Tighten Tighten the transmission filler tube bracket nut to 10 N.m (89 lb in).
14. Install the air cleaner resonator outlet duct. Refer to «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000) .

Scheme 14

Scheme 15

1. Raise and suitably support the vehicle. Refer to «LIFTING AND JACKING THE VEHICLE»(ref-188480-S19457848752005090300000) in General Information.
2. Remove the exhaust manifold pipe nuts.
3. Lower the vehicle.
4. Remove the spark plugs. Refer to «SPARK PLUGS»(ref-159085-S02952502512003111400000) .
5. Remove the heat shield bolts, and shield from the exhaust manifold.
6. Remove the exhaust manifold bolts, manifold, and gasket.
7. Discard the gasket.
8. Clean and inspect the exhaust manifold. Refer to EXHAUST MANIFOLD CLEANING AND INSPECTION .

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