POSSIBLE WATER PUMP LEAKAGE CORRECT GASKET PART NUMBERS

VEHICLES AFFECTED: ALL WITH TRANSVERSE MOUNTED HT4100 ENGINES

1987 HT4100 engines are equipped with a redesigned water pump that incorporates a sealing bead stamped into the sheet metal body of the pump. This pump requires the use of a specific, non-beaded, gasket(see Figure 1). The 1985 and 1986 models used a water pump without the stamped sealing bead. These pumps required a gasket with a bead of sealant applied directly to the gasket, refer to Figure 1. Each gasket is specifically designed to be used with the corresponding water pump. If the pumps and gaskets are interchanged, there is a possibility of leakage.

Individual water pump gaskets can be ordered using the following part numbers:

PART NO.

NON-BEADED WATER PUMP GASKET (1987) 1635792 BEADED WATER PUMP GASKET (1985 AND 1986) 1627915

These gaskets are designed to be used on the particular style of water pump, not necessarily year of the car.

A service kit consisting of a pump and gasket is available through GM Parts Division. This kit contains the beaded water pump and the non-beaded gasket and supersedes the previous design. This kit can be installed, on any transverse mounted HT4100 engine. The part number for this kit is:

PART NO.

WATER PUMP AND GASKET KIT 3634653

A note has been included in the Parts Catalog to alert Technicians to be aware of which. pump design is being used on the particular engine they are servicing. NOTE: Some 1987 service engines may be built with a 1986 style water pump.

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.