WATER PUMP SERVICE NEW DESIGN WATER PUMP

The 1983 HT4100 engine incorporates significant design changes to the cooling system. The coolant hose between the coolant reservoir and the water pump used on 1982 engines has been eliminated resulting in a new design water pump for 1983 applications. A water pump kit (P/N 3634580) will be available from GMWDD for servicing both 1982 and 1983 models which consists of a water pump, gasket, three thermostat housing "O" rings, rubber cap, hose clamp and instruction sheet. This kit, however, will not be available at the beginning of the 1983 model year. The following instructions outline a service procedure detailing how the 1982 HT 4100 water pump (P/N 3634552) can be modified to service the 1983 HT 4100 engine until the 82/83 kit is available.

Service Procedure

I. Fabricate a plug as shown in Figure I or obtain equivalent. The fabricated plug shown consist of: a section of 3/8" I. D. rubber hose (cut from 25' bulk hose, P/N 9439162) approximately 2 1/2" to 3" long; a 3/8" dia. shoulder bolt with the threaded portion cut off; and 2 appropriately sized hose clamps.

II.The plug should be assembled to the 1982 water pump at the 3/8" dia. nipple near the top center of the water pump as shown in Figure 2 prior to installation and when installed, positioned so that it does not interfere with other engine components.

NOTICE: A specific radiator cap (P/N 6410427) must be used on the 1983 cooling system. Failure to use the correct radiator cap may cause redueed engine cooling and result in engine damage.

For warranty purposes, use labor operation number J3480 at 2.1 hours and add .2 hour for fabricating plug.

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.