CHICAGO (CBS) — There’s no sign that the CTA intends to put its newest ‘L’ cars back in service soon.

Forty of the cars were in service — and CTA had taken delivery of 52 more — when they were suddenly withdrawn on Dec. 16, because of multiple flaws in the wheel assemblies.

READ MORE: Woman Dead After Being Stabbed On South Wacker Drive Downtown

Each of the assemblies are being subjected to a battery of X-rays and stress tests.

CTA President Forrest Claypool said the testing is being done locally, as well as at the Bombardier assembly plant in Plattsburgh, New York.

Trains of the new ‘L’ cars were seen on the Red Line last week, but Claypool said they were out of service and merely going to and from X-ray sessions.

Claypool said that, so far, the agency’s engineers and those from the manufacturer have not come up with solutions, although they have isolated the problems to parts from a specific supplier.

READ MORE: At Least 2 Killed, 18 Wounded In Weekend Shootings In Chicago

Asked if he fears that the new ‘L’ cars could be lemons, he said he does 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.

MORE NEWS: Woman Shot, Wounded On North Avenue On Cusp Of Humboldt Park, Logan Square

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.