Dear Tom and Ray:

My daughter bought a 2005 Kia Sorento nine months ago, and was given an extended warranty by the dealership. A week ago, it started running badly, so she took it back. The technician said two cylinders were not working. He said they found a piston ring in the oil pan, and corrosion on the top of one piston. Now they are telling her that the damage was caused by an "unknown foreign object" that got into the engine. They are calling this a "road hazard," and won't pay for the large repair bill. Does this diagnosis make sense to you guys?

-- Jennifer

RAY: An "unidentified foreign object" got in there? Like what? Leonid Brezhnev?

TOM: There are only a few ways that a foreign object could get into the cylinders, Jennifer. And they're all unlikely.

RAY: One is through the air filter. But even the lousiest air filter is supposed to filter out objects larger than about 50 microns (that's about two-thousandths of an inch). So if a foreign object large enough to cause catastrophic engine failure snuck in the through the air filter, the innards of the air filter would be destroyed.

TOM: So ask the guy to give you the air filter. You may need it as evidence at a later date.

RAY: The second way an unidentified foreign object could get into the cylinder is with the gasoline. Again, most cars have several gas filters, not to mention fuel injectors with tiny nozzles. So there's no way anything comes in that way.

TOM: Then there's the oil, which also is filtered. And I've never run across a foreign object in a bottle of oil.

RAY: The final possibility is that something could have been dropped into one of the spark-plug holes while a spark plug was out. But unless you've had some reason to have the spark plugs removed in the first nine months of owning the car, that's impossible, too.

TOM: Here's my guess as to what happened: A piece of a piston skirt broke off. (That's the lower part of the piston.)

RAY: That's not a "road hazard." That's a "used car hazard." And it would have happened because an engine was badly overheated, mismanufactured, poorly maintained or old and worn out. In any of those cases, they owe you an engine, since they gave it a warranty.

TOM: They're not happy about that. They may have offered this "extended warranty" themselves, rather than buy it from an outside company. And they're loath to spend another 2,000 dollars on a car they already consider sold. But T.S., Eliot.

RAY: Given the evidence you've presented (and assuming your daughter is not withholding any crucial information about losing her keys while her boyfriend changed the spark plugs), the dealership's story sounds pretty unlikely.

TOM: My advice would be to have the car towed somewhere else, and let someone with no financial stake in this matter examine it. Ask for his opinion on what happened and his thoughts on their UFO (unidentified foreign object) theory.

RAY: If his opinion is the same as ours, you can try presenting your case once again to the original dealership -- this time, with evidence. But ultimately you may have to take them to small-claims court to get them to pay for your engine.

TOM: But an independent second opinion is the first order of business, Jennifer. Good luck to you.