ALUMINUM INTAKE MANIFOLD CORROSION (REPAIR PROCEDURE)

MODELS AFFECTED: 1986 BROUGHAMS

This bulletin replaces bulletin T-89-119 which should be discarded. The labor time has been increased to include R&R of the intake manifold.

Some 1986 Broughams equipped with 5.0L (VIN Code Y) engines used an intake manifold 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 the intake manifold is not necessary. Intake manifold deterioration may be repaired following the procedure listed below under "Intake Manifold Repair Procedure:"

Service Gaskets Revised:

The service intake manifold gaskets have been revised to delete the insulation sheath. When using the revised gaskets it is essential that sealer, P/N 1050026 or equivalent, be applied to both sides of the gasket where it contacts the cylinder head and the intake manifold. Please revise your 1986 Service Information Manual to reflect this procedure change.

Intake Manifold Repair Procedure:

Intake manifold gasket deterioration as described above may result in corrosion pitting of the aluminum intake manifold.

It is not necessary to replace the intake manifold for this condition. Use an 80% aluminum epoxy, such as Devcon "F" or equivalent, to fill the corrosion pits in the aluminum intake manifold.

Service Procedure:

1. Remove intake manifold.

2. Thoroughly clean corroded area using a wire wheel to remove all aluminum oxide.

3. Remove all remaining grit and dust with compressed air, or thoroughly wash in a solvent.

4. Mix epoxy with hardener according to instructions. Apply with a two inch putty knife or similar flat straight-edged tool. A heat gun can be used to shorten curing time.

5. After hardening, smooth surface down to its original machined surface using a single cut flat mill file. Inspect for voids and refill if necessary. Surface may be smoothed further using 320 grit sandpaper with a sanding block.

IMPORTANT: Before reinstalling the intake manifold it is essential that sealer, P/N 1050026 or equivalent, be applied to both sides of the intake manifold gasket where it contacts the cylinder head and intake manifold. Refer to Figure 1.

Parts are currently available through GMSPO.

For warranty purposes use Labor Operation T6384 at 3.2 hours with an add time of .2 hour if the vehicle is equipped with cruise control.

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.