Engine - Preventing Premature Main Bearing Failures

BULLETIN NUMBER:
SB98-O1-LOO8

ISSUE DATE:
JULY 1998

GROUP:
ENGINE

AFFECTED VEHICLES
1997-98 HOMBRE (TH) PREVENTING PREMATURE
MAIN BEARING FAILURE

SERVICE INFORMATION

Condition:
There have been several reports of some 4.3L V6 engines experiencing main bearing failure. In most of these cases, this condition has occurred soon after an inlet manifold Removal & Replacement procedure.

Possible Cause:
Excessive tightening torque to the inlet manifold bolts, affecting crankshaft main bearing clearances.

Correction:
During the reinstallation of the inlet manifold, refer to the Workshop Manual for correct service procedures.

NOTE:
If the inlet manifold attaching bolt torque and tightening sequence specified in the Workshop Manual are not strictly adhered to, crankshaft main bearing bore alignment can be distorted with crankshaft main bearing failure being the end result.

SERVICE PROCEDURE:

Refer to the published Workshop Manual Section: Engine Mechanical - 4.3L, "Intake Manifold Installation (lower)" for detailed service procedures.

^ Always follow the proper bolt tightening sequence for each of the THREE torque steps.

^ Do not exceed the specified tightening torque of each step.