Mercedes-Benz Recalls Older ML, GL, R-Class Vehicles Over Brake Booster Corrosion

Supplied by Continental Tire Americas, the booster in question bears part number A1644310627. The main and only purpose of the booster is improved braking performance. As implied, a brake booster amplifies hydraulic pressure to the brake master cylinder, as in the device that converts the brake pedal's force into hydraulic pressure by feeding brake fluid into the brake circuit. Boosters also help drivers exert considerably less force when braking.

Mercedes-Benz AG started investigating the described problem back in July 2021, following a field report from outside the United States describing an instance in which the driver experienced abnormally low brake force support. Right off the bat, the Stuttgart-based manufacturer determined that the brake booster was impaired by corrosion.

One case was identified in the United States in March 2022, prompting the safety boffins at MBUSA to file recall documentation with the National Highway Traffic Safety Administration. Recall number 22V-315 from May 2022 comprised a staggering number of vehicles, namely 292,287 units of the ML, GL, and R-Class from 2006 to the 2012 model year. The million-dollar question is, why did MBUSA issue a second recall for 15,604 vehicles?

Turns out the owners did not receive notification letters despite MBUSA including the recall statuses properly in all Mercedes-Benz dealer systems, on the company's website, and on the NHTSA's website. Merc filed a separate recall for said 15,604 vehicles based on discussions with the federal watchdog.

Fortunately, there have been zero reported crashes, property damage, injuries, or worse caused by this defect. Dealers have already been instructed to inspect and – if necessary – replace the brake booster. The remedy part differs from the original brake booster in one notable way, that being the lack of an aesthetic rubber sleeve around the housing.

Regarding which versions of the ML, GL, and R-Class are affected, the list kicks off with the 320 series. 320 used to mean turbocharged V6 diesel in Mercedes vernacular, with the 320 CDI of that era making 215 horsepower and 398 pound-feet (540 Nm) between 1,400 and 2,800 revolutions per minute. Remember when AMGs were advertised as Mercedes-Benz alphanumeric designation AMG? At the other of the spectrum, the R 63 AMG and ML 63 AMG are also recalled.

The R 63 is one of the rarest AMGs of all time, with Merc producing 322 units for the entire world. In a similar fashion to the ML 63, the go-faster minivan packs 6.2 liters of naturally aspirated V8 muscle. R-Class production would come to a screeching halt in 2017, whereas the ML 63 soldiers on as the GLE 63 with a twin-turbo V8 with mild-hybrid assistance.

As of May 2024, the GLE 63 S 4MATIC+ SUV is $127,700 sans destination charge. You'll have to pony up $129,050 at the very least for the coupe-styled sibling, whereas the GLS 63 SUV is $145,850 from the outset. From a displacement of 4.0 liters, the force-fed lump develops a stout 603 horsepower and 627 pound-feet (850 Nm) of twist.