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Reports that some 1999-2001 GM 2.2L VIN 4 engines tend to generate a droning noise that is especially noticeable at approximately 950 rpm after cold start up.

Engine Builders: There have been reports that some 1999-2001 GM 2.2L VIN 4 engines tend to generate a droning noise that is especially noticeable at approximately 950 rpm after cold start up.

GM has identified the source as a natural resonant vibration of the air conditioning alternator drive belt. A revised belt, p/n 12575450, made of a different material may reduce or eliminate the noise.

Engine Builders: The AERA Technical Committee offers the following cylinder head gasket and cylinder liner protrusion caution on 1958-’89 Mack E6 675 and ENDT 673 diesel engines. Two different thickness cylinder head gaskets are supplied by Mack, one standard thickness cylinder head gasket and a .008˝ (.203 mm) thicker head gasket.

Caution must be used because both the cylinder head gaskets share the same cylinder fire ring. Adjusting the cylinder liner protrusion, depending on the thickness of the head gasket being used maintains the correct clamp load on the cylinder fire ring. This step is necessary for proper operation and long durability.

When using the standard thickness cylinder head gasket, use a cylinder block counter bore depth of .184˝-.188˝ (4.673-4.775 mm). Use the standard thickness head gasket #553GB433A that is identified by its orange colored sealing beads, and is also identified by notches located on the left front and left rear corners of the head gasket.

Engine Builders: The AERA Technical Committee offers the following information regarding a revised lash adjuster for 1992-2003 Hyundai engines. This lifter revision applies to all of the engines shown in the chart (Figure 2) used by Hyundai. The new larger hole lash adjuster has been installed on engines produced beginning October 2000.

The oil hole opening was doubled in size from .059˝ (1.5 mm) to .118˝ (3.0 mm), see Figure 1. The new lash adjuster assembly may be installed on the engines, if replaced as a set within the engine. It is not recommended to mix the two different adjusters.

A new hydraulic lash adjuster (p/n 24610-33050) with a larger oil hole has been released to reduce engine noise. AERA is aware of at least one aftermarket source at this time.

For information on receiving all of AERA’s regular monthly technical bulletins and other association services and benefits, call toll free 888-326-2372 or e-mail info@aera.org.