CHICAGO (CBS) — The Chicago Transit Authority is still working on tests for an equipment problem that forced its new fleet of train cars to be taken out of service, according to a published report.

The CTA had pressed 40 new 5000-series cars into service on the Pink Line, and 52 more had been delivered, when they were all suddenly withdrawn because of multiple flaws in the wheel assemblies.

Afterward, each assembly was subjected to a battery of X-rays and stress tests, which are being conducted locally and at the assembly plant for manufacturer Bombardier Transportation in Plattsburgh, N.Y.

The CTA and Bombardier aren’t telling the Chicago Tribune’s John Hilkevitch much else about the defects, which were found in steel wheel-baring casings called “journal bearing housing.”

CTA President Forrest Claypool said previously that the agency had isolated the problems to parts from a specific supplier.

Asked earlier this month if he feared that the new ‘L’ cars could be lemons, Claypool said he did not.

CTA is still locked in litigation over “accordion-style” buses manufactured by North American Bus Industries that were removed from service in 2009 after less than five years of service, because of multiple recurring defects, particularly in the supports for the accordion.

Bombardier has had recent quality issues with rail cars being delivered to the Swedish, French and German state railroads. Those deliveries have resumed.

The delivery of the new 5000-series ‘L’ cars has been halted until the testing is complete and a solution is found. CTA has agreed to purchase 706 of the cars.

Until enough of the new cars are in service, the 43-year-old 2200-series cars will continue in operation.

Ironically, the 2200s also had a problem as deliveries were made in 1969 and 1970, with the third rail shoe used to collect power. That problem was resolved quickly and replacements were made. The cars have remained in continuous service since then.