WHITE OR BLUE SMOKE-COLD START AND/OR ENGINE COOLANT LEAK

INTAKE MANIFOLD GASKETS

Model and Year: 1986 5.0L V-8 ENGINE (VIN CODE Y) --------------

TO: ALL CHEVROLET DEALERS

A mid-year change has been made in the intake manifold gasket. Early 1986 models with 5.0L (VIN Code Y) engines used a gasket with an insulating sheath applied to the gasket in the area that contacts the intake manifold. This insulating material is dark orange in color.

There have been cases where the sheath in the area of the coolant passages has deteriorated which resulted in a leak. Most coolant leaks are external; however, there have been cases where coolant leaks have been internal. When investigating a loss of coolant, and a leak is not obvious, remove the intake manifold and examine the gasket for deterioration and evidence of an internal leak in the area of the coolant passages. If an internal leak is found, replacement of heads, blocks or intake manifolds is unnecessary.

The service gaskets will, in the near future, be revised to delete the insulation sheath. When using one of the revised gaskets, it is essential that sealer, part No. 1050026 or equivalent be applied to both sides of the gasket where it contacts the cylinder head and the intake manifold.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.