Case of the Month: The Vandalized Cobalt

Jan 2, 2013 by

GEI was assigned to examine a vandalized Chevrolet Cobalt and determine the cause of its engine damage.

The vehicle was inspected at the repair shop.  The exterior was in poor condition as several scrapes, scratches, and dents were found to the body panels.   The exterior condition was not the result of vandalism.

The interior of the vehicle was also briefly examined.   The interior was also very poorly maintained.   Rotting food, clothes, toys, and other items were found in the interior.

The vehicle was in the process of being repaired, for a second time, when we inspected it. A previous engine repair proved to be ineffective.

We observed that a contaminant was introduced into the fuel delivery system by way of the fuel filler tube.   The vehicle’s fuel door could be easily opened from the outside of the vehicle.   No interior releases or external locks were found that would have prevented easy access to the fuel filler area.   Anyone walking by the vehicle could have easily poured a fluid or powder into the fuel system via the fuel filler.   However, no residue or other evidence of a contaminant in the fuel filler area was found at the time of the inspection.

Components of the fuel system, including the fuel tank, had been removed.   The engine was intact; however, the date-of-loss cylinder head had been removed from the vehicle and was available for inspection.

Traces of a fuel system contaminant were found throughout the cylinder head fuel intake passageways and on the intake valve stems and heads.

The partially solid remains of the contaminant appeared to be a substance much like “Fix-A-Flat” or a similar flat-tire-repair-in-a-can compound.   Two samples of the contaminant were obtained from the fuel tank for later analysis, if necessary.

The samples were delivered to Garsto for secure storage.

The lighter and more volatile components of the tire sealant compound were absorbed by the gasoline.   This allowed the solvents and glue to pass through the fuel filter and travel through the fuel system.   It was then sprayed out of the fuel injectors and settled on the intake valves.  After the engine cooled, the glue solidified.   The valves were then stuck in their valve guides. When the engine was restarted, the valves remained stuck open, when they should have closed.   The pistons then struck the open valves, which bent the valve stems, further preventing the valves from closing because the valve stems no longer slid up and down in the tight-tolerance valve guides.

The repair facility attempted to repair the damages caused by the contaminant, however, the repairs were unsuccessful.   The mechanics did not recognize the cause of the bent valves, so a set of new valves met the same fate as the originals.   In order to properly repair the damages, the entire fuel system, including the fuel tank, needed to be thoroughly cleaned, (and some components replaced) to entirely remove all traces of the contaminant.   Additionally, the cylinder head needed to be disassembled to determine which of the internal components were damaged (like the valve guides) and to determine whether the cylinder head could be cleaned or also needed to be replaced.

In conclusion, a flat-tire-repair-in-a-can contaminant was introduced into the fuel system via the fuel filler tube.   The liquefied and volatile portions of the contaminant passed through the fuel system, including the fuel filter,

(pictured above) solidified on the valves, gluing some of them open, which were then struck by the pistons, bending the valve stems, which then further damaged the valve guides.

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