10 used cars to avoid

The Audi Q5 has been a hit since it debuted in 2009. This versatile little crossover looks and drives great. But Consumer Reports data, which come from customer surveys, show that owners have had problems with the engine cooling system, power equipment, audio system and squeaks and rattles, among other things. If you buy a used Q5, consider one that is certified pre-owned and comes with a warranty.

Check Listings: Find used Audi Q5s in your area

The BMW 3-Series commands respect. It is the gold standard for performance sedans. Too bad the 330i and 335i models, which are in the sweet spot of the 3-Series range, have proved so unreliable. Serious problem areas include the fuel system, major and minor engine components, body hardware and audio system. The 2012 BMW 3-Series is all-new.

Check Listings: Find alternatives to the BMW 3-Series in your area

The Chrysler Town & Country and its corporate twin, the Grand Caravan, are American mainstays. Dodge has sold millions of them, despite their tendency to break down. It doesn't matter what model year, their reliability is terrible across the board, according to Consumer Reports. And it's not just minor things; the transmission, engine components, suspension, brakes and electrical and fuel systems are all problematic.

Check Listings: Find alternatives to the Chrysler Town & Country

Jaguar is the most improved brand in J.D. Power & Associates 2012 Initial Quality Study, having leaped from 20th place last year up to second. The sexy, luxurious and sporty XF is a huge improvement over the S-Type it replaced in 2009. If only it were reliable. Its transmission, drive system and electrical system are among the major components prone to failure.

Check Listings: Find alternatives to the Jaguar XF

The Jeep Grand Cherokee is rugged and can go practically anywhere. At odds with this seemingly indestructible nature is a track record for failure. Both the V6 and V8 models are unreliable, though recent V6 versions have fared somewhat better. Problem spots include the cooling system, climate control system, drive components, brakes, power equipment, body hardware and minor engine parts The jury is out on whether a comprehensive redesign for 2011 affected reliability.

Check Listings: Find alternatives to the Jeep Grand Cherokee

It seems incongruous that a high-priced luxury car could be unreliable, but that's certainly the case with Mercedes' midsize crossover. The 2006 and 2007 models are particularly bad, according to Consumer Reports. They suffer from major engine problems, faulty electrical systems, broken body hardware, transmission woes and a host of other issues.

Check Listings: Find alternatives to the Mercedes-Benz M-Class

The MINI Cooper S and the slightly larger Clubman S have a more potent engine than their respective base versions. More power means more problems. Consequently, the S engines — turbocharged or supercharged, depending on the year — are seriously problematic. In addition, transmissions, fuel systems and body parts that squeak, rattle and break will also upset owners.

Check Listings: Find alternatives to the MINI Cooper

The fact that a Nissan is on this list proves that no automaker is invincible, not even one with a great track record for reliability. A 2009 redesign of this sporty 2-seater has unfortunately brought a host of problems that didn't exist before, particularly related to the engine and transmission. The drive system, suspension and brakes are also failure-prone.

Check Listings: Find alternatives to the Nissan 370Z

Porsche is a perennial top dog in J.D. Power & Associates quality studies. These race-bred sports cars are known for being almost bulletproof. But not all of them are. The 2006 Porsche 911 appears to be an anomaly, with problematic electrical and engine cooling systems. It's hard to say for sure whether the 2006 model is alone in its deficiencies. Still, 2007 and 2009 models are reliable, as are the Porsche Boxster and Cayman.

Check Listings: Find used Porsche 911s in your area

This cute cult car is a letdown when it comes to reliability. Consumer Reports lacks data for models from 2008 through 2011, but 2007 and older models are riddled with issues. Both hatchback and convertible versions of the New Beetle have so many problems that it's easier to list the areas that are sound: the suspension, brakes, exhaust and climate control system. Everything else will eventually need repair.

Check Listings: Find alternatives to the Volkswagen New Beetle

Matthew de Paula wanted to be an automotive journalist ever since reading his first car magazine in grade school. After a brief stint writing about finance, he helped launch ForbesAutos.com and became the site's editor in 2006. Matthew now freelances for various outlets.