General Motors' Position on Use of Surface Conditioning Discs
The AERA Technical Committee offers the following information regarding the use of grinding discs as obtained from the General Motors Corporation. When cleaning engine gasket sealing surfaces, surface conditioning disks (typically constructed of woven fiber or molded bristles) which contain abrasives, such as a high amount of Aluminum Oxide, are NOT RECOMMENDED. The information contained in this bulletin supercedes any previously published GM service information regarding the use of surface conditioning disks and pertains to all current and previously manufactured engines.
The use of such surface conditioning discs dislodges Aluminum Oxide from the discs and metal particles, which can lead to premature engine bearing failure. In some cases this failure occurs in as little as 1,000 miles or less after the repair has been made.
Surface conditioning discs may grind the component material and imbed it into the disc. This can result when more aggressive pressure is applied during the cleaning/grinding of the gasket surface.
Do not use abrasive pad/bristle devices to clean the gasket surfaces of engine components. Abrasive pads or devices should not be used for the following reasons:
*Abrasive pads will produce fine grit that the oil filter will not be able to
remove from the oil. The grit that cannot be filtered out has been known to
cause engine damage. Abrasive pads can easily remove enough material to
round cylinder head surfaces. This has been known to affect the gasket's
ability to seal, especially in the narrow seal areas between the combustion
chamber and the coolant jackets.
*Abrasive pads can also remove enough material to affect cylinder head,
block, oil pan rail, and intake manifold runner flatness, which can cause
coolant and oil leaks. It takes only about 15 seconds to remove .008" of metal
with an abrasive pad.
To clean such gasket mating surfaces, General Motors reccommends the use of a razor blade or plastic gasket scraper. When cleaning gasket surfaces, please note the following:
*When using a razor blade type gasket scraper, use a new razor blade for
each cylinder head and corresponding block surface. Hold the blade as
parallel to the gasket surface as possible. This will ensure that the razor
blade does not gouge or scratch the gasket surface.
*Do not gouge or scrape the combustion chamber surfaces.
*Do not gouge or scratch any engine-sealing surface during the cleaning process.
The appearance of the gasket surface is not "critical" the feel is. There is a possibility that there will be some indentations from the gasket left in the cylinder head after all the gasket material is removed. The new gasket will fill these small indentations when it is installed.
The AERA Technical Committee