A worker fixes a logo to a Volkswagen car.

Volkswagen is telling U.S. dealers to stop selling its most popular cars until transmission fluid leaks can be fixed.

The order covers about 25,000 Jetta, Passat, Beetle and Beetle convertible models equipped with 1.8-liter, four-cylinder engines and automatic transmissions, spokesman Scott Vazin said Wednesday. They were built after Feb. 1.

An "O-ring" that links a transmission fluid line to a cooler can fail and cause leaks, potentially causing a fire. Vazin says no fires or crashes have been reported. VW plans to replace the defective parts.

About half the cars remain on dealer lots. Vazin says VW is working with the National Highway Traffic Safety Administration on how to fix the cars that have been sold.

He says owners with questions about their cars should contact their dealers.

Vazin expects parts to be available to make the repairs in two weeks or less. The simple repairs should take about a half-hour, Vazin says.

The stop sale order comes a month after VW announced its biggest safety recall of its Chattanooga-made Passat.

Volkwagen said in March that about 160,000 of the sedans for model years 2012 and 2013 may have a low-beam headlight bulb issue that could lead to reduced visibility.

The voluntary recall, the second for the Tennessee-assembled car since its production started in 2011, impacts about 150,000 Passats in the U.S. and another 10,000 in Canada.

VW said it's possible in instances where the car hood is closed roughly or dropped from a certain height that the resulting vibration can cause a headlight bulb to lose electrical contact.