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Mercedes-Benz harbors some mixed press regarding its history with reliability. While its engines and drivetrains are typically bullet-proof, many other issues sometimes slip through the cracks. It’s easy to get caught up in the stigma that German cars are unreliable. However, brands like BMW and Mercedes-Benz constantly push for new technology, so of course, there will be complications. Nevertheless, these are some of the most unreliable Mercedes-Benz that just plain did not live up to the usual excellence of the brand.

2006 E350

2006 mercedes benz e class reveal
2006 Mercedes-Benz E-Class Reveal | TORU YAMANAKA/AFP via Getty Images

Mercedes’ E350 from 2006 was big and comfortable. Though acceleration required more encouragement than usual, it delivered smooth power and drove like it was on clouds. It also offered primitive adaptive cruise control, where the car could adjust its distance to other cars on the road while in cruise control. Unfortunately, the E350 garnered multiple hundreds of complaints via the NHTSA

Owners cite debilitating issues with the fuel system. An owner in South Carolina had an issue with leaking gas, where they had to replace the fuel tank, pump, fuel line, and seals. It happened a second time as well, around 104,000 miles. Another owner complained of complete brake failure. To the car’s credit, ESP and ABS errors showed on the instrument cluster. Later models are among the most reliable luxury cars on the market, but the 2006 is one of the most unreliable Mercedes-Benz ever made.

2007 S550

2007 mercedes benz s550 parked outside in New York
2007 Mercedes Benz S550 | Getty Images

The 2007 S550 offered unrivaled cabin sound deadening, big plush leather seats, and rapid acceleration. Its 5.4-liter V8 sent 382 horsepower to the rear wheels via a 7-speed automatic transmission. It hit 60 mph in 5.3 seconds and completed the quarter-mile in 13.7. The S550 also had a horrendous problem with its electronics that was systemic and not recalled by Mercedes. It became one of the most unreliable Mercedes-Benz because of this problem. 

Several drivers complained of their S550 driving normally before suddenly collapsing into limp mode. Service advisors recommend replacing the car’s Engine Control Unit (ECU), which is a $2,000 part. Other owners mention the engine’s balance shaft wearing out, which loosens the timing chain, which leads to broken valves. 

2015 C300

2015 mercedes benz c class coupe on display
2015 Mercedes-Benz C-Class | Getty Images

Which Used Mercedes Is the Most Reliable?

The 2015 C300 looked aggressive compared to its previous generation. Unfortunately, its bark was worse than its bite. The C300 used a turbocharged inline-four that pumped out 241 horsepower via a 7-speed automatic transmission. At 3645 curb weight, 241 horsepower leaves some acceleration to be desired. Like others on this list, it had faults that simply couldn’t be ignored.

Owners complained of the sunroof panel detaching from the car while driving on the freeway. Thankfully Mercedes recalled this part. Mercedes chalked it up to poor bonding application and replaced the panel for free. The car also had problems with airbag inflators exploding, sending sharp shards into passengers, and steering locknut failure. This car had a host of other problems that made it one of the most unreliable Mercedes-Benz ever.

Like any other brand, Mercedes-Benz has had its hiccups. While the engine and drivetrain are solid thanks to overengineering, other parts of the car may fail spectacularly. That said Mercedes-Benz makes reliable cars, it just takes some research to find the right one. Nevertheless, a Mercedes-Benz pairs best with a decent warranty and a big pocketbook.