Metro plans to spend $215 million over the next five years to replace a long-troubled series of rail cars, according to transit agency documents and officials.

The 100 cars in Metro’s 4000-series fleet have been plagued by problems with brakes, lights and air conditioning, and the transit agency is opting to replace them years ahead of schedule.

Metro board member Tom Downs once called the 4000-series rail cars a “fleet full of dogs,” saying the chronic breakdowns were “killing” the agency.

Made for Metro by the Italian manufacturer then known as Breda Costruzioni Ferroviarie, the 4000-series cars were delivered in the early 1990s and would ordinarily have been due for an overhaul. But the transit agency says it will forgo that work, which would cost about $1.5 million a car, and instead buy new cars under a contract it has with Kawaski to build its new 7000-series rail car.

The plans, described in documents prepared for Metro’s board meeting Thursday, were confirmed by Dan Stessel, a spokesman for the transit agency.

Metro signed a contract with Kawasaki for 428 rail cars at a cost of $886 million, and the first batch of those 7000-series cars is expected to arrive this year. About 300 of the new cars are to replace the 1000-series cars, the agency’s oldest model, and the rest will be added to the fleet to accommodate the opening of the Silver Line.

To replace the 4000 series, Metro is exercising an option in its contract with Kawasaki to purchase additional 7000 series cars. But it will take six to eight years to process and manufacture the new order, and during that time the transit agency will continue to use the 4000-series rail cars.

Metro has about 1,100 rail cars in its fleet, and they have been delivered in batches designated with a series number since the system began running in 1976.

The 4000 series is not the only model that has caused the transit agency problems.

Last year, a friction ring — part of the braking system on a rail car — fell from a 5000-series rail car, damaged two more rail cars, and shut down service along the downtown core of the Orange and Blue lines for hours.

Brake parts also fell off a 2000-series rail car and a 3000-series rail car, leading to delays of more than two hours.

The 1000-series cars were involved in the Red Line crash in 2009 in which nine people were killed. The National Transportation Safety Board recommended that Metro stop using the 1000 series.