DIESEL CYLINDER HEAD PRECHAMBER CRACKS

DURING THE SERVICE OF 6.2L DIESEL CYLINDER HEADS, THE OBSERVANCE OF HAIRLINE CRACKS MAY BE NOTED IN THE PRECHAMBER AREA. CRACKS ON THE FACE OF THE PRECHAMBER START AT THE EDGE OF THE FIRE SLOT. FROM THE EDGE, THE CRACKS PROCEED TOWARD THE CIRCULAR IMPRESSION OF THE HEAD GASKET BEAD. THESE CRACKS ARE A FORM OF STRESS RELIEF AND ARE COMPLETELY HARMLESS UP TO A LENGTH OF 5 MM 3/16. CRACKS LONGER THAN THIS ARE APPROACHING THE HEAD GASKET SEALING BEAD AND SHOULD BE REPLACED WITH THE PROPER PART NUMBER. REFER TO TRUCK SERVICE BULLETIN #83-B-26 FOR PROPER PRECHAMBER. THE SKETCH BELOW OF A PRECHAMBER DISPLAYS BOTH ACCEPTABLE AND NONACCEPTABLE CRACKS. (SEE ILLUSTRATION)

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.