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How to Change the Exhaust Manifold Gasket in a 2002 GMC Envoy

The exhaust manifold is the area of the vehicle where exhaust gases from the cylinders accumulate prior to being passed into the exhaust pipe. A poor manifold gasket, which is located between the manifold and engine cylinder, can lead to an exhaust leak, indicated by a ticking or tapping noise that is much louder when the engine is cold. As the engine warms up, the noise will dissipate. The procedure will vary slightly depending upon whether your 2002 Envoy is a V6 or V8 engine but, independent of the engine, the repair can be completed with the engine in place.

Instructions

1

Disconnect the cable from the batterys negative terminal. Lift the vehicle and support it securely on jack stands.

2

Apply penetrating oil to the exhaust pipe-to-manifold studs and nuts from beneath the vehicle. The bolts are typically rusty. Wait a little while to allow the penetrating oil soak into the bolts.

3

Remove the nuts retaining the exhaust pipe to the manifold, using a socket wrench. On a V8 engine, there will be two exhaust manifolds which are more easily accessed with the front tires and the inner fenderwalls removed, although it is not absolutely necessary.

4

For a V6 Envoy, unplug the oxygen sensor electrical connector. On a V8 Envoy, detach the spark plug wires and remove the spark plugs from the manifold side being worked on. If both manifolds are being removed, detach all spark plug wires and remove all spark plugs.

5

Remove the three heat shield nuts using a socket wrench then remove the heat shield. Place the heat shield aside.

6

Perform the following if you are working on a V8 Envoy. The procedure is dependent upon the side of the vehicle where the manifold is located. For the right side, remove the air cleaner assembly and the oil dipstick. Unbolt the dip stick tube bracket and move the dipstick tube. Remove the EGR valve by removing the pipe to intake manifold mounting bolts, the EGR valve mounting bracket-to-cylinder head bolts and the EGR pipe-to-exhaust manifold mounting bolts. On the left side of the vehicle, simply disconnect the electrical connector from the engine coolant temperature sensor, which is at the front of the cylinder head above the number one spark plug.

7

Remove the exhaust system manifold bolts using an open-ended wrench. Detach the manifold from the cylinder head. Remove the exhaust manifold gasket.

8

Clean the mating surfaces on the cylinder head and the manifold using a gasket scraper to remove all carbon deposits. Check the manifold for cracks and make sure the bolt threads are clean and undamaged.

9

Install a new gasket to the mating surfaces between the cylinder head and the manifold.

10

Install the manifold on the cylinder head. Apply heat-resistant thread locking compound to the bolt threads and then start tightening the bolts by hand. Tighten the bolts with a torque wrench in three passes, starting from the center bolt and working your way to the ends. Tighten the bolts to 18 foot-lbs.

11

Reinstall the remaining components in the reverse of removal, tightening the heat shield to 80 inch-lbs. using a torque wrench. Start the engine and check for exhaust leaks.

Posted by Unknown at 7:30 AM

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