S10/T10 Blazer 4WD V6-4.3L VIN W (1997)
Crankshaft Main Bearing: Technical Service Bulletins
Engine - Premature Main Bearing Failure
File In Section: 6 - Engine
Bulletin No.: 87-61-22
Date: March, 1998
INFORMATION
Subject:
Premature Main Bearing Failure
Models:
1996-98 Chevrolet and GMC C/K, M/L, S/T, G, P Models
1996-98 Oldsmobile Bravada
with 4.3L V6 Engine (VINs W, X - RPOs L35, LF6)
There have been several reports from the field (TAS) of some 4.3L V6's experiencing premature engine main bearing failure. In most of these cases, this
condition has occurred soon after an inlet manifold R&R procedure.
In 1996, the Gen 1 V6 engines were re-engineered to incorporate "vertical" inlet manifold to cylinder head attaching bolts. If the inlet manifold bolts are
over torqued, the crankshaft main bearing bore will be distorted, eliminating the necessary clearance for proper oil film.
Notice:
IF INLET MANIFOLD ATTACHING BOLT TORQUE AND TIGHTENING SEQUENCE ARE NOT STRICTLY ADHERED TO, PER THE
SERVICE MANUAL, CRANKSHAFT MAIN BEARING BORE ALIGNMENT CAN BE DISTORTED WITH CRANKSHAFT MAIN BEARING
FAILURE BEING THE END RESULT.
Important:
1.
Always follow published inlet manifold service procedures.
2.
DO NOT overtorque inlet manifold to cylinder head attaching bolts.
3.
DO NOT deviate from the published bolt tightening torque sequence.
