Engine - Head Bolt Threads Pull Out of Engine Block
SI B11 06 06
Engine
May 2012
Technical Service
This Service Information bulletin supersedes SI B11 06 06 dated June 2006.
[NEW] designates changes to this revision SUBJECT
Head Bolt Threads Stripping Out of Block During Engine Reassembly
MODEL
[NEW] All with aluminum engine block
[NEW] SITUATION
While performing the torque procedure on the cylinder head during engine reassembly, the head bolt threads strip out of the block. Typically this occurs during the repair of an engine that has been overheated.
CAUSE
Overheat condition has weakened the structure of the aluminum block assembly in the area of the bolt threads.
[NEW] PROCEDURE
In cases where an engine needs to be disassembled due to an overheating event, the following steps should be taken:
Before removing the cylinder head, loosen and retorque each head bolt to ensure thread strength and integrity.
If the engine block threads strip (pull out of the engine block) during the retorque, replace the engine block with piston or complete "short" engine assembly as determined and supported by the repair/replacement cost analysis.
If all head bolts achieve correct torque, proceed with cylinder head removal. Once removed, use a straight edge on the block surface, as well as the cylinder head, to determine if any deviation caused by the overheat is present. If applicable, be aware of any protrusion of the cylinder liners above the surface of the engine block.
Note:
Some engines and engine blocks require TeileClearing approval before replacement.
[NEW] WARRANTY INFORMATION
For covered repairs where the approved BMW repair instructions allow for the repair or replacement of a part, component, or assembly, a repair must be performed as long as the cost of repair does not exceed 75 percent of the cost of replacement of the part, component or assembly.
