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, areNOT RECOMMENDED. The information contained in this bulletin supersedes 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 filter 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 recommends 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. The 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.