Engine Builders: The AERA Technical Committee offers the following information on an exhaust noise for 2002-2004 GM 4.2L engines. This noise may be coming from under the vehicle or from the engine compartment. The cause of this noise may be from one or two known sources.
The first location that may be causing this type of noise is exhaust leaking between the exhaust manifold and cylinder head mating surfaces. To determine if this is the location of the mentioned noise, spray a non-flammable liquid around the manifold-to-head mating surfaces. The noise should change slightly and/or the liquid will blow away from the leaking area. This noise may be resulting from the manifold mounting bolts loosening during normal engine operation.
If the manifold is the source of noise, remove the manifold and install a new exhaust manifold gasket (p/n 88890561) and mounting bolts (p/n 11588261 – qty. 11). The new mounting bolts have the proper pre-applied adhesive on the threads. DO NOT use any additional thread lock material. Torque the bolts in the sequence shown in Figure 1, to 15 ft.lbs., three separate times.
The second location to consider for an exhaust type noise/rattle may be coming from a ground out condition caused by a transmission oil cooler line(s) contacting the catalytic converter. To resolve this condition, raise the vehicle and carefully reposition the transmission oil cooler line(s) to provide .393″ (10 mm) clearance between the exhaust catalytic converter and the line. Replace the transmission oil cooler line if any damage is present.
Engine Builders: The AERA Technical Committee offers the following information on camshaft identification for 1998-2005 Volkswagen 2.0L AEG, AVH and AZG engines. These engines are similar but use different camshafts.
To assist in identifying the cams when servicing these engines, Volkswagen has placed visual markings between specific lobes. Refer to the illustration and chart in Figure 2 above to identify the stamped numbers and letters between intake and exhaust lobes.
After camshaft identification, verify it is the correct cam for the head and engine.
Note: When new lifters have been installed, the engine must not be started for about 30 minutes. Hydraulic compensation elements must settle (valves will strike pistons).