During any service repair on 2024 and earlier GM models that involves cylinder head removal, installation or replacement, it’s critical that all dirt, debris and coolant be cleaned from the engine block cylinder head bolt holes. Any foreign material not removed from the bolt holes may result in damaged threads or improperly tightened fasteners, and may lead to damage to the engine block or other components.
In some cases, the engine block may crack due to debris, dirt or coolant that is left in the cylinder head bolt holes of the block. Foreign material that is in the bolt holes during cylinder head assembly can create a hydro-lock condition that will over-pressurize the casting column of the threaded hole in the block, causing the casting to crack or break.
The head bolt threads also may be damaged if there is foreign material in the bolt holes when installing the cylinder head. (Fig. 1)
Fig. 1
Cylinder Head Installation
Before performing any repairs involving cylinder head installation or replacement (Fig. 2), be sure to:
- Clean all dirt, debris and coolant from the engine block cylinder head bolt holes.
- Clean bolt holes using spray solvent and compressed air.
- Inspect and repair, if necessary, the threads of the head bolt holes following the appropriate Service Information procedures.
Fig. 2
The Cleaning and Inspection Procedures will be updated in the Service Information to include additional information on the proper process to follow during cylinder head installation to help prevent damage to the engine block.
Debits for warranty repairs will be issued for any failure or damage to the vehicle due to improper service, non-return of parts, or after the inspection results by the Warranty Parts Center.
For additional information, refer to Bulletin #23-NA-141.
– Thanks to Bryan Salisbury
