The trains, a key moneymaker for Amtrak in the Boston-New York-Washington corridor, were pulled from service Tuesday after inspectors discovered cracks in brackets that attach shock absorbers to the locomotives.
Amtrak officials said they feared one of the assemblies — known as yaw dampers — could fall off a moving train, damaging its underside or another train. The function of the yaw dampers is to prevent swaying, which can increase wear and tear to rails and train wheels.
The problem is the latest in a summer-long series of financial and public-image blows to the struggling passenger railroad.
Amtrak President David Gunn said the trains would remain out of service for at least a few days. If a proposed temporary fix doesn't work, the trains could be sidelined for weeks.
The first problem was discovered Monday during a periodic maintenance inspection of an Acela Express train in Boston.
Of the next 10 train sets inspected, eight had similar problems, Amtrak spokesman Bill Schulz said. Each train set includes two locomotives, and each locomotive has four yaw dampers.
Inspections were continuing on the seven other Acela Express trains, which are capable of reaching a speed of 150 mph.
Gunn met Tuesday afternoon with representatives of Bombardier of North America and France's Alstom Ltd., the train's manufacturers, to design a repair plan.
"We're working with the manufacturer on a temporary fix," Gunn said. "We've got to make sure it's safe." He said he believes the repairs will be covered under the contract with the manufacturers.
The planned temporary fix involves a new part that Amtrak and the Federal Railroad Administration will begin testing this week.
"If the remedy is satisfactory to Amtrak and to federal rail safety officials, a return of the train sets to revenue service would be a matter of days, as opposed to weeks," the railroad said in a statement.
Bombardier spokeswoman Carol Sharpe said the company is committed to helping Amtrak find a solution that will get the trains running again.
Even before the latest discovery, Amtrak had announced that all 18 of the high-speed trains need repairs and modifications. The passenger railroad declined to accept delivery of a 19th train, citing modifications that were not made.
Already this summer the railroad suffered a cash crisis so severe that it needed $205 million from the government to avert a nationwide shutdown.
Last month an Amtrak train from Chicago to Washington derailed in Maryland, injuring more than 100 people. The train engineer reported seeing a kink in the tracks that could have been caused by excessive heat, and investigators found the rails were more than two feet out of alignment.
"They just happen to have all their stars aligned the wrong way right now," said Scott Leonard, assistant director of the National Association of Railroad Passengers, a rail advocacy organization.
Passengers have been told for safety reasons, they're being put on the slower, cheaper trains to New York and Boston, reports CBS News Correspondent Dan Raviv at Washington's Union Station.
"The train was packed and I had to stand," said Julio Francisco of Newark, N.J., after arriving in Philadelphia on Tuesday morning. Other passengers arriving in Philadelphia later Tuesday said nobody had to stand on their trains.
Other Amtrak trains that serve the busy Northeast Corridor, including Acela Regional and Metroliner service, are not affected. "We're bringing as much equipment as we can into service to make up for the shortfall," Schulz said.
Amtrak pledged to credit passengers for the difference in ticket prices between Acela Express and the trains they take. Passengers were encouraged to check departures by visiting Amtrak's Web site or calling (800) USA-RAIL.
Acela Express is Amtrak's premier service in its busiest market. More than 10,000 people ride the swift trains on a typical weekday, enjoying amenities such as a pub-style cafe car and electrical outlets at every seat.