Coeficient of linerar expansion.

[William]

The 6 cylinder engine used in the 2003-up Trailblazer also has that problem. I found a broken off bolt head in the garage one day. Since you can't see the manifold it is not that obvious. Lerned later what the problem was. Good thing we had extended the warranty. They replaced all bolts and the manifold; 7 hours labor. It can be worse-if the bolts snap off flush with the head the engine has to be removed to repair it.