Even though it exited the U.S. truck and bus engine market four years ago, Caterpillar (CAT) has been hit with at least 15 lawsuits over mechanical problems and fires experienced by engines it previously made.

Plaintiffs in the cases allege that CAT bus and truck engines made between 2006 and 2010 had defective emission control systems, which led to frequent breakdowns. A number of engine fires are also cited. There are no reports of injuries linked to the CAT engine problems, but plaintiffs say that the engine failures often stranded people for hours until alternative transportation could be arranged, the Wall Street Journal noted.

CAT has settled with plaintiffs in one lawsuit, paying $46 million to settle claims that a ship fire in Alabama was sparked by one of its defective engines. Last year, CAT paid $900,000 to a Texas school district to settle a suit over bus engines. The owner of Minnesota-based CH Bus Sales said that he ordered 60 buses with CAT engines seven years ago, but that many of the buses couldn’t be dispatched on long trips due to unreliability. He also said that two buses were destroyed by engine fires.

Caterpillar says it “is addressing various claims relating to alleged performance issues.”

In Friday morning trading, Caterpillar stock edged slightly higher. CAT stock closed at $106.65 per share on Thursday.

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