An alleged manufacturing defect in hundreds of school buses purchased by metro Atlanta school districts has left taxpayers on the hook for expensive repairs and left children at times stranded in broken-down buses, local school district officials say.

“There have been many cases where these buses failed while on routes carrying students,” Cobb school district officials said in an email to The Atlanta Journal-Constitution.

In those situations, another bus has to be located, then sent to pick up the students while they wait.

In Atlanta Public Schools, the system has spent more than $1.5 million repairing the engines and buying extra buses.

The problems stem from diesel engines with new technology intended to reduce pollution, and they aren’t limited to the Atlanta area. Some bus service companies have sued the manufacturer, and other districts are threatening legal action.

Two related school bus service companies in Illinois filed a federal lawsuit against the company that makes the engines —Illinois-based Navistar International Corporation — for racketeering and fraud in connection with what it says are identical issues. They’re seeking millions of dollars in damages.

Navistar also faces a federal class action lawsuit in connection with alleged problems with other engines with similar emission-controls technology used in ambulances, garbage trucks, tractor trailers and other vehicles.

Along with Cobb and Atlanta schools, Gwinnett and Fulton county schools also purchased buses with the diesel engines. DeKalb had a single bus with the engine in question.

Navistar spokeswoman Lyndi McMillan declined to comment in response to inquiries from the AJC. But in court filings seeking to dismiss the Illinois lawsuit, Navistar said the plaintiffs had waited too long to file the suit and that many of their claims don’t meet the legal definitions of fraud or a racketeering conspiracy.

Atlanta Public Schools is considering taking legal action against Navistar in coordination with other districts, Atlanta transportation executive director John Franklin said.

In Atlanta Public Schools, about half of the 132 buses with these engines — most of them purchased around 2008 or 2009 and no longer under warranty — have undergone “significant repairs,” Franklin said. The repairs have cost an estimated more than $300,000 to date — plus about $1.5 million for new buses to augment the district’s fleet and compensate for the time the Navistar buses are out of service.

Gwinnett County, the state’s largest public school district with 1,900 buses, purchased 204 with the Navistar engines in 2004, school district officials said. All but seven of them are still in use.

School district officials said they’ve had similar trouble with the engines.

Gwinnett typically rebuilds its bus engines to get more mileage out of them and to keep from having to replace vehicles. Typically, those bus engines are good for another 120,000 miles. But when the engines on Navistar buses are rebuilt, they last only 65,000 miles.

Gwinnett stopped buying the vehicles in 2006.

Cobb County school officials said the engines have been an ongoing problem for them. The most common are Exhaust Gas Recirculation cooler failures, injector failures and camshaft failure. They could not estimate how much they've spent on the maintenance work.

Fulton County owns more than 240 buses with the diesel engines in question, according to records obtained under the state Open Records Act. District officials did not respond to interview requests from the AJC.

Franklin, the Atlanta schools transportation director, said the engine troubles often come to light after a bus breaks down while in use, leaving children waiting on the side of the road.

“It’s an inconvenience felt by a lot of folks,” he said.