Pop Goes the Piston

This bulletin was released by Chevrolet, but the warning really applies to a multitude of vehicles. Some customers may complain of an SES light and a constant engine misfire. In some cases, they may also note a tick/knock noise.

During diagnosis, the technician may find no compression on the misfiring cylinder(s) with 100% leakage into the crankcase. This may be the result of an aftermarket ECM calibration/components and detonation that lead to a melted piston.

Before disassembly of the engine, perform the following:

1. If a lighted borescope is available, inspect the top of the related cylinder’s piston through the spark plug hole to determine if any of the pistons are melted.

2. Inspect the dome and dome edges.Inspect for aftermarket components such as an exhaust, ignition, high performance controller, etc.

Example of a burn-through on a hypereutectic piston.
<p>Example of a burn-through on a hypereutectic piston.</p>

Tags: General Motors  GM  Piston 
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