INTAKE MANIFOLD GASKET REPLACEMENT

MODELS AFFECTED: 1985-1988 DE VILLE AND FLEETWOOD, 1986-1988 ELDORADO AND SEVILLE, AND 1987-1988 ALLANTE

With the introduction of the 4.5L V8 engine for the 1988 model year, some revisions to the cylinder head water passages have dictated changes to the intake manifold gasket. Due to the consequences of mismatched heads and gaskets, the cylinder head water passage shape should always be matched with the appropriate gasket.

As shown in Figure 1, all 1982-1987 4.1L engines except the Allante, should use the gaskets in kit #3634619 (except as noted in Figure 1). This gasket is intended for use on engines with the large water passage as indicated. Use of these gaskets on 1988 4.5L engines may result in internal coolant leakage.

1988 4.5L engines incorporate a revised coolant passage and require gaskets included in kit #3634723. Past model 4.1L service engine assemblies built during the 1988 and subsequent model years may incorporate this cylinder head revision and, therefore, require the #3634723 gaskets. Inspection for the appropriate gasket will be required. Use of these gaskets on 4.1L engines with the original design large coolant passage cylinder heads will result in internal coolant leakage.

1987 and 1988 4.1L port fuel injection Allante engines incorporate a taller intake port which demands gasket kit #3634660.

Cylinder Head Intake Manifold Bolt Holes

The intake manifold bolt holes indicated in Figure 2 are blind holes. The remainder of the intake manifold attaching holes are open on the bottom. If the blind holes become impacted with material or are not threaded to the bottom of the hole, the bolt will bottom out before the required "crush" has been applied to the intake gasket to afford an effective seal. Technicians should assure that these tapped holes are clear by chasing the threads with an M8 x 1.25 bottoming tap. The holes are intended to be threaded all the way to the bottom. If this is not evident, continue to tap until this condition exists.

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.