This bulletin applies to 2011-2014 Chevy Cruze vehicles. Some customers may comment on a loud engine rattle or knock type noise, or the accessory drive belt and the lower crankshaft pulley has come off.
An inspection may reveal a loose or broken bolt from the crankshaft pulley and/or flywheel bolts, causing them to make a noise or leaving the engine.
According to GM, broken or loose bolts at the crankshaft pulley and/or flywheel are the result of excessive engine overspeed.
The cause of the higher than normal rpm’s are achieved by shifting the transmission from a higher gear to a lower gear at a high rate of speed. This allows the wheels to drive the engine at a higher rpm than it is capable of handling.
To identify if the engine rpm’s were higher than the design load limits, use GDS2 and select Data Display, Overspeed Data table.
Check to see if the data shows that the engine has been run at too high of an rpm level. Any speed higher than 7,500 rpm is too excessive and could result in engine damage.