ENG. BLOCK HEATER LEAK-INSTALL REDESIGNED BLOCK HEATER

Subject: ENGINE BLOCK HEATER LEAKS

Model and Year: 1976-92 LIGHT DUTY TRUCKS

Some owners of 1976-1992 light duty truck engines may experience a leaking condition from the engine block heater. This condition may be caused by the block heater losing torque because the yoke, which secures the block heater, has cracked. This could cause a loss of engine coolant.

The block heater brass yoke may crack due to stress corrosion where it contacts the stainless steel Crossbar. The yoke is stressed or cracked from over torquing the hold down screw (Figure 1, "6"). Corrosion in the stressed area is accelerated due to the dissimilar metals.

To correct this condition, a redesigned block heater should be installed. The yoke material (Figure 1 "3") of the block heater was changed from brass to stainless steel. The stainless steel is a higher strength material which reduces the possibility of stress corrosion and galvanic potential.

SERVICE PROCEDURE:

Follow the "ENGINE BLOCK HEATER REPLACEMENT" instructions in section 9E ENGINE BLOCK HEATER of the appropriate Service Manual.

CAUTION:

The gasket "O" ring seals between the block heater and the block. Excessive tightening is not necessary. The torque specification is 1.6 - 2.2 N.m. (15.0 - 20.0 lbs. in.)

The revised engine block heater (P/N 10154624) can be used in any light duty truck, gas or diesel engine, where an engine block heater is used.

SERVICE PARTS INFORMATION

PART NUMBER DESCRIPTION Qty/Veh ----------- ----------- ------ 10154624 Engine Block Heater 1

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Description Labor 0p. ----------- -------- Heater, Engine Block - Replace R4600

Use applicable labor time guide for labor hours.

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.