Looks like Mercedes has a MUCH MUCH bigger issue on their hands and may be purposefully allowing vehicles that are let's say "borderline unsafe" on the roads since Mercedes is needing to re-designing the part for replacement in approximately ONE MILLION affected vehicles worldwide. Considering designing/related testing issues and likely supply chain problems that many companies have been facing in recent times, they probably won't have the parts for some time (which is why they are requiring another inspection/part replacement within two years - see more discussed below).
I know, for a fact, that my vehicle failed the comprehensive testing in my discussions with the dealer, but as I have experienced and discussed with people at Mercedes, if cars fail the tests they are now re-testing the vehicles (sometimes more than once) and miraculously many (some have reported that practically all that are re-tested) are subsequently released and owners are told that the vehicle "passed". Some people have however learned that Mercedes apparently later modified the subsequent test standards, to in essence enable more/nearly all to pass, for the time being that is...
If you had your vehicle tested and were told it "Passed" most people think "great" and go on with their things not knowing what was tested and thinking that they don't need to have the car repaired. However, this is far from what is really happening. If you actually look at the paperwork, as the dealerships were "supposed to" provide the owners with a follow-up letter with the service records that announced that the vehicle passed, where later in the letter it states that those owners - must have the car inspected again within two years or completely stop driving the vehicle after two years. Furthermore, that notice also references that if you sell the vehicle you "must provide" this warning notice to the prospective buyer. So your vehicle "may" have passed (as it may have failed and was then retested and retested to get closer to passing with changed parameters of the testing), but is it really safe??? Remember this is your braking system!!!
The problem is much more complicated and damaging for Mercedes, as Mercedes has ultimately admitted - in writing to the U.S. Department of Transportation that; "Estimated percentage with defect: 100 %"
In being forced to announce a DO NOT DRIVE / STOP DRIVING NOTIFICATION, it seems that Mercedes has been experiencing many more test failures than they estimated, and it then resulted in ongoing costs to provide rental / loaner vehicles, had resulted in extensive expenditures - especially when you consider that there are approximately one million affected vehicles worldwide
. So it seems that in order to reduce such expenses on these older vehicles, they have apparently "secretly" modified the testing standards/parameters (and seemingly not notified many/most dealers, nor the US Department of Transportation). Such would then, for the time being, create less concern as more people are told that their vehicles passed the tests... it would then importantly buy-time, while help reduce many associated expenses that Mercedes has been facing (rental, storage at dealers, etc). Additionally, it could then make it "appear" in recall reports that Mercedes provides to the US Department of Transportation (and other countries) that the issue isn't that bad.
There are several Class Action Lawsuits that have been filed in the United States, where at least one filing alleges that Mercedes knew about the problem and created an internal Technical Service Bulletin over a decade ago concerning such brake booster problem, but failed to take action early on and allowed the problem to get much worse. With a million affected vehicles, one can only imagine the costs associated with the problem, while the more time that passes, the more vehicles come off the road, the more people would tend to attribute it to parts simply wearing, and the lower the values of the vehicles over time. Also if the vehicle gets into an accident, how many situations are realistically going to be inspected so thoroughly, that this specific part will be then specifically tested, traced as defective, litigated, and determined to be the cause/contributing cause? Mercedes had an army of lawyers on call to fight claims, but in this situation, it seems likely that someone (with a conscious) ultimately leaked info to force the recall.
It is certainly extremely rare for the U.S. Department of Transportation (through its safety agency NHTSA) to push/order a manufacturer to announce anything as drastic as a STOP DRIVING NOTIFICATION... unless the issue is determined to be extremely serious! And if such recall is so concerning, it is in Mercedes's interest to make it "appear" that it isn't so bad....with failing cars instead being re-tested to pass (despite no repairs being made).
Assuming that the reporting noted in the Class Action Lawsuit has some merit with regards to Mercedes knowing of this problem more than a decade ago, with the huge population of vehicles involved, the passing of time... without conducting the repairs needed.... is often a calculation that automakers and their "bean-counting" accountants access.... and where they put expenses in front of people with calculated "acceptable losses". Over and over again this has been proven to be the way vehicle manufacturers handle things going back 50 plus years when it first really became exposed in the Chevrolet Corvair and Ford Pinto design flaws. Where for example Ford was found to have handled manner by hiding information, delaying taking any action, and cutting corners, and literally calculating the number of lost lives and injuries expected and the costs associated with those losses vs. repairing all the vehciles! Sadly this type of scenario has been repeated by many manufacturers, and it is likely that all / practically all vehicle makers do this.
Check out more details and the discussion regarding Mercedes's handling of this recall, and several references to Mercedes created reports concerning the recall, at this link:
Mercedes brake booster recall - my R Class failed safety...