Disney maintenance workers had replaced the "quick exhaust valves" in an area known as Zone 7 the night before the accident and tested them several times before opening the attraction, Disney officials said. But a leak in the new valves caused one of the main brakes to fail July29, allowing the train to roll through Zone 7 and hit the train that was still sitting in brake Zone 8.
Disney had chosen to install Legris-brand valves on the tracks because parts from the original manufacturer, Intamin, were not available, said Rob Doughty, a Disney spokesman.
After the accident, Disney opted not to use either brand, instead replacing all 320 valves on the coaster with Parker valves that have been used on Disney coasters for about 30 years.
Just before the accident, Disney also had replaced the hoses on the braking system, which functions with air pressure. The Division of Occupational Safety and Health, which oversees safety at permanent amusement parks, reported that "an ongoing problem with the air line leaking due to the age of the parts" prompted Disney to replace those hoses.