Mercedes Working to Brake Quality Erosion

Marina Naumann is driving her Mercedes-Benz E-Class down steeply twisting Camps Bay Drive, just south of Cape Town, South Africa.

Suddenly an alarm sounds and the instrument panel flashes: “Long Stop Brake Failure-Stop Car.” Naumann would do that — if she could. The brake pedal has gone soft as if there is no connection to anything.

The E-Class's high-tech electro-hydraulic Sensotronic Brake Control (SBC) braking system switches to backup mode, but braking power is minimal. Shaken, Naumann steers the Mercedes to a stop on the only slice of near-flat gradient in sight.

Naumann is not alone in having electrical problems with her E-Class. In late March, Mercedes issued a global recall of all 1.3 million cars equipped with the Robert Bosch GmbH-built SBC system.

The system, an early attempt at “by wire” control of brakes that eliminates the physical connection between the brake pedal and the brakes themselves, first was introduced on the current-generation 320 SL and later fitted to the E-Class (W210 series) and CLS.

Mercedes says in its recall that SBC may shift prematurely to the hydraulic backup function due to deterioration of the wiring harness or premature failure of the hydraulic pump.

As a consequence, the driver has braking power sufficient to stop the vehicle, although greater brake pedal pressure is required, and the brake pedal travel will be longer.

Although the SBC brakes can be fixed, the sting of worldwide publicity surrounding the recall has given Mercedes' once-impregnable quality reputation another beating.

The fall from grace can be traced back to the early 1990s decision to retreat from the reality of its slogan, “Engineered like no other car,” combined with more recent moves to incorporate innovative electronic features.

The result is a quality nightmare that has deeply tarnished the Mercedes brand and sent the marque plunging in customer-satisfaction ratings.

Mercedes once was famous for its over-engineered vehicles. But a new, “leaner” engineering philosophy was introduced by then Mercedes chief Juergen Hubbert and DaimlerChrysler Corp. CEO Dieter Zetsche, who at the time was head of Mercedes research and development.

Their goal was to help Mercedes cut cost while meeting the challenge of competition — particularly from the supremely efficient Japanese.

The new system cut as much as two years from the previously unhurried 7-year development process for any all-new Mercedes model. At the same time, the auto maker added a raft of niche models and greatly expanded the range at both ends.

What followed was a shift from an engineering-dominated product-development process and culture to a marketing-driven environment that resulted in the disappointing W210 E-Class, controversial A-Class and the quality-challenged, U.S.-built, M-Class SUV.

The decision to adopt innovative electronic features for the new SL and E-Class now is viewed as overkill. Coming so soon after the auto maker's seminal mid-1990s engineering shift to develop new models according to a pre-determined budget, the mandate only amplified Mercedes' increasingly stretched engineering resources.

For decades, the E-Class has been the nucleus from which Mercedes' entire model range radiates and, because of the numbers — about 300,000 sold annually — the model has been the company's greatest profit generator.

But hurt by the critical quality-degradation publicity, especially in Europe, sales of the E-Class have plunged this year, taking Mercedes into the red. Production for the first three months was down 32% to 56,615 units.

Mercedes' 100,000-mile (161,000-km) diesel-power world record attempt earlier this year wasn't just about confirming the ability of its new V-6 turbodiesel, or selling diesel technology to the U.S.

On a far wider front, the record-setting run, involving three E320 CDIs selected at random off the assembly line, was intended to reinforce to the world the E-Class' superior overall quality and reliability.

The idea of using a record run to shore up a car's or brand's reputation isn't new. Ford Motor Co. Australia Ltd. went the same route for its XP Falcon in 1965.

Michael Kramer, head of development for the C/E-Class, tired of hearing his cars disparaged, devised the plan last September. Mercedes now believes the record run was a success on all three levels.

“We want to prove the electronics of our cars are of the same quality as the mechanical parts,” says Thomas Weber, Mercedes board member responsible for Research & Technology and Development, on hand to witness the run at the DC test track in Texas.

“The (SBC) recall sent a message to the customers that they can trust us. If we have a problem, they know we will fix it.”

Weber admits Mercedes' desire to be first meant implementing an excess of electronic features without fully understanding the potential problems.

“We realize now that many of the ideas we adopted came from consumer electronics,” he says. “That was a mistake. We now know they were not all suitable for cars.”

Mercedes did test the components, he says, although suppliers conducted some of the testing. But the auto maker now realizes components cannot be tested themselves.

“You need to test the whole car to see how they are integrated together in one environment,” Weber says. “That was our biggest lesson.

He also says Mercedes needs to rethink its timeline in order to determine which electronic innovations are important to customers and decide how fast the systems can be adopted.

“We don't need to be as fast as possible; that's not our idea,” he says.

As for the brake problem that afflicted Naumann's E270, Weber says it was caused by vibration that allowed the wiring harness to work loose, triggering a shutdown reaction from the engine's electronic control unit.

The ECU then slipped into a special failure mode that deactivated the SBC system. The recall fixes the harness more securely, and the modification now is being applied to production cars, he says.

Tellingly, however, this year's upcoming all-new S-Class, originally engineered with the SBC system, will use conventional hydraulic actuation instead.

How many flawed cars has Mercedes replaced? Weber is not specific. “Only a few,” he says.

Even so, Mercedes customers demand nothing less than the luxury maker's historic reputation for perfection — the company's bottom line depends on it.