"We've seen reports of cracking and leaking. We have not identified a risk to motor vehicle safety," Sherwood said.
The National Highway Traffic Safety Administration said it has received 37 complaints of faulty valve stems but no crashes or injuries have been reported. In 23 of the complaints, the vehicle had more than one valve that was "severely cracked or cracked and leaking" and needed replacement.
Eleven complaints said the valves led to lost tire inflation and required the tire to be replaced.
The vehicles with the valve stems include the Ford F-150, Mustang, Edge, Fusion, Expedition, Explorer, Focus and Escape, and the Mercury Grand Marquis, MKX, MKZ, and Milan. The valves are made by Topseal Automotive, a subsidiary of Shanghai Baolong Automotive Corp.
NHTSA said it has opened a preliminary evaluation to "assess the scope, frequency and safety consequences" of the alleged defect in the Ford tires. Defect investigations can lead to vehicle recalls.
The highway safety agency opened a separate investigation in May into 23 million valve stems manufactured by Shanghai Baolong in 2006. NHTSA said more than 4,700 complaints have been filed because of the valve stems, including allegations of a fatal rollover crash involving a 1998 Ford Explorer in November 2007.
On the Net:
Ford Motor Co.: ford.com
National Highway Traffic Safety Administration: nhtsa.dot.gov