CORRECT INTAKE MANIFOLD GASKET INSTALLATION. GMC Truck GMC K Pickup

VEHICLES AFFECTED: 1987-1990 LIGHT DUTY TRUCKS W/4.3L, 5.0L, 5.7L TBI ENGINES

This bulletin is for informational purposes only, and should be used as a guideline if it becomes necessary to replace the intake manifold gaskets on 4.3L, 5.0L and 5.7L TBI engines.

With the introduction of TBI engines, a change was made to the intake manifold gasket by adding a restrictor plate to the rear coolant passage of the gasket in order to direct coolant to flow from the front of the intake manifold, under the TBI section of the manifold (heats TBI to prevent throttle plate icing) and exit out of the heater hose pipe at the rear of the manifold (See Figure 1).

Anytime it becomes necessary to replace the intake manifold gasket, it is essential that the gaskets be properly installed. If the gasket is installed backwards i.e., with the restrictor plate at the front of the engine, the engine will overheat. When diagnosing overheat conditions, the proper installation of the gasket can be checked without removing the manifold. Both the 4.3L, 5.0L and 5.7L gaskets have metal locator tabs that can be seen sticking out from between the manifold and the cylinder head. When installed correctly, the tab on the 4.3L will be to the rear of the engine and the tab for the 5.0L and 5.7L engine will be to the front of the engine (See Figure 1).

Object Number: 75393 Size: FS

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.