Drivers of certain older Ford cars and SUVs have been warned that their vehicles present "unreasonable safety risks" due to a timing belt defect that could lead to sudden power loss or engine seizure.

The National Highway Traffic Safety Administration has escalated its defect investigation into approximately 135,000 Ford Fiesta, Ford Focus, and Ford EcoSport vehicles, all equipped with 1.0L engines from various model years between 2014 and 2021.

The agency says it has received 355 reports detailing incidents where a low engine oil pressure warning light appeared just before a complete loss or reduction of motive power while driving. The agency's initial probe suggested that timing belt material can degrade, creating debris that clogs the mesh oil pump pick-up screen, ultimately resulting in reduced engine oil pressure.

The investigation indicates that these failures can occur without sufficient warning, making a loss of power or engine seizure imminent, even in vehicles that have undergone proper and routine oil maintenance.

”Based on NHTSA’s analysis of the data, failure rates, information provided by Ford, preliminary engine teardown analysis, and precedent recalls regarding loss of engine oil pressure with the presence of driver facing warnings, (the agency) believes there is an unreasonable risk to motor vehicle safety,” the agency wrote.

Data shows an average failure mileage of approximately 70,000 miles, with 98% of failures occurring before the suggested 150,000-mile timing belt replacement.

Ford, which has discontinued all three models, offered no immediate comment on the upgraded probe.

Drivers have reported significant issues, including one incident on a major Delaware highway where a 2017 Ford Focus "lost all power and the engine began to sound like a tank" within an eighth of a mile after the oil pressure light illuminated. Some owners have faced thousands of dollars in engine repair costs.

NHTSA's move to upgrade the probe to an engineering analysis is a mandatory step before it can compel Ford to issue a recall.

In June, Ford informed NHTSA it was implementing a "non-safety customer satisfaction program" for global vehicles with a 1.0L Fox Classic Timing Belt, reducing the maintenance interval to 100,000 miles or six years.

Ford is also offering reimbursement to eligible customers who previously paid for engine repairs or replacement due to a timing belt-related issue, though it remains unclear which U.S. vehicles are covered by this program.