Mercedes-Benz and the ‘OM651 case’


Some carmakers invest millions in order to measure and increase Customer Satisfaction.

Today the manufacturers must be able to measure themselves “1-2-1” with their Customers, with transparency: thanks to the web any single Client could become a powerful promoter or a devastating detractor.

This is one of the reasons why carmakers should be ready to confront themselves with the Social Media, the blogs and the tam-tam of the Internet!

But sometimes someone makes an own goal! This has happened to Mercedes-Benz with the types “C” and “E”, 220 & 250 Cdi versions, equipped with the new engine OM651 De22.


This is a stunning “common rail” diesel engine, among the first to mount a piezoelectric fuel injection system by Delphi. From the beginning this new motor has expressed several failures to the apparatus of the electrical power system, causing repeated breakdown of the cars… on the road.

Although unpleasant, it is understandable that new vehicles could go haywire: even the human body – evolved in 250,000 years – sometimes it breaks causing pain and worries. Imagine a car with only 100 years of history …

The technicians in Stuttgard at the beginning has decided to buffer the emergency by replacing only the single injector involved; with repeated interventions several times on the same car; with … several breakdowns.

Who has never been into trouble in a highway during the night – with children on board – may not realize the hardship, danger and anger that this entails.


But also a fault in the home garage, or along the ring road during rush hour when it’s raining and you’re late for an appointment, are not the medicine for high blood pressure …

In Italy, to the angry Customers, were given hasty explanations, as: “the Italian diesel at the gas stations has a quantity of sulfur which prevents the proper operation of the injectors” or “errors were found in contact with the power plug because the damaged injectors were disassembled several times”.

It is interesting to speak with taxi drivers or small fleet owners.

Online reputation? Someone in the Marketing or at the Customer Service – at the HQ – has underestimated the power of the web.

All the M-B enthusiastic fans in hundreds of communities, clubs and blogs all over the world, began to exchange concerns and information about their misadventures with the OM651 – which in the meantime have been added problems to the distribution chain and water pumps.


Factory tests and tests carried out “on-the-road” directly on the cars of the customers have shown that the old system of magnetic injection (Delphi) was much more reliable than the piezoelectric (although less modern, less efficient, more polluting, and more thrifty in fuel consumption).

Enough to force the german engineers to engage the reverse gear, and decide to introduce a “downgrade technology” abandoning the new piezoelectric technology on this engine.

Despite rumors on the Internet and various legal actions undertaken by customers, no recall campaign or official communication has been addressed by the Customer Service to the owners of defective vehicles.


It seems that “automatic service actions” – carried out behind his back of customer – are regularly developed: if by chance a M-B owner bring his car into a workshop for a service or a maintenance, he can be found with the whole apparatus of fuel injection replaced.

Without giving – it seemsno explanation of what really constitutes the intervention, that is, as customers told us: “replace the new piezoelectric injectors with the old magnetic ones, installation of a plant for the recovery of diesel return, replacement of the engine electronic control unit, and replacement of the acoustic cover placed over the engine”.

It is a burdensome service intervention, expensive, no doubt aimed at the safety of the customer.

Mercedes-Benz have built his reputation on perceived quality and quality of service, with a marketing refined, with a guideline which states: “when in doubt, replace”.

So why – with the OM651 case – not talk openly with their customers, preferring keep things vague – if not worse – falsehood?

The real Customer Service starts from… transparency!

M-B: please, don’t let your reputation is badmouth: Internet is… waiting in ambush!

And … DealerRater, Carfolks, Edmunds, Women-Drivers and dozen of others sites ‘watch over’ the consumers!

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  1. Jukka says:

    I have a 2011 MB E-Class 250 Cdi.

    It broke down last summer on our summer holiday while we were driving in Germany on our way to Finland. It was a Sunday and we had a ship to catch to Finland and the whole thing was a complete nightmare with wife, two small children and a dog in the car.

  2. Peter says:

    The incredulous part of this is that we had the same issues with the OM641 motor when it was launched over 2 years ago! Initially the launch was delayed because Merc knew there was a problem with the injectors, but elected to launch anyway and rather deal with any issues that resulted. Funny how they also blamed our diesel quality. Bottom line: Mercedes-Benz knowingly launched a defective product into various markets and LIED blatantly to customers when the vehicles started coming back!!!!!

  3. Gianluca Ventura says:

    What I read in this article here is ABSOLUTELY TRUE!
    As owner of a mid 2011 BlueEfficiency 6 speed Amg SportPack E220 Cdi Coupé, I’m directly victim of this ‘action’ performed by Mercedes-Benz with all Om 651 (220 – 250) Piezo diesel engines equipped cars.
    Like a stupid young boy, I was trapped into the confusing fog between ‘service action’ and ‘recall action’, and convinced – even if my opinion was negative – to bring my car (running perfectly till that moment) to an MB dealership here in Milan (Mercedes-Benz Milano) for a so called ‘update action’ of my injection.
    An ‘update’ which was, honestly speaking, exactly the contrary, because it was A TECHNICAL DOWNGRADE of the car.
    Why? Because they explant your modern and expensive Piezo injection system and put under your car bonnet a conventional outdated Magnetic one, turning ‘de facto’ your 220 Cdi or 250 Cdi into a 200 Cdi, which has always had the Magnetic system combined with only one turbo (220 and 250 have double).

    So, instead of really solving the problem of piezo units breakdowns, MB prefers to take an easier – for them – solution, which is astonishing if U think that Daimler Group is number 1 in the world: going back to a previous generation of injectors, with ACTIONS PERFORMED AUTOMATICALLY DURING REGULAR MAINTENANCE OF THE CAR, as if the car were theirs.
    So, U don’t know, but U bring your golden handles car to MB workshop and have in return one with iron handles in return.
    Nice, isn’t it?
    That’s the reason of the confusing fog I was writing in the beginning of this comment: nobody would accept such an exchange without receiving at least a financial compensation for it.

    My work, as a motor journalist, is testing vehicles since 1990 and I receive daily tech press info reporting about – let’s say – new technical discoveries. That’s why, when back in 2008, I received this ) press release, as happy owner of a 2007 sedan C220 Cdi, I started thinking about buying a new Mercedes-Benz car equipped with this revolutionary engine. And, in 2011, I did it.
    But after that crazy service action – performed also in a very bad way with the car returning to dealership a couple of times for heavy diesel leaks in engine compartment – my car isn’t the same anymore:

    1) Fuel consumption rose 10%;
    2) Average noise increase 8 dbA;
    3) Less power (poor performances);
    4) Sometimes car doesn’t start up in the morning or does it with difficulties;
    5) But, what it’s worst, it behaves like a KANGAROO! Yes, when U release gas pedal, engine begins bumping slightly with rpm gauge going up and down 100 rpms.

    I brought my car again to MB dealership and had it back 10 days later with this sentence: “all cars equipped with Om 651 engine and manual gearbox are like this now.”
    U N B E L I E V A B L E!

    I gave them a car perfectly running and had back a broken one that they do not know how to fix anymore. Period.

    One more thing.
    As far as I know, U cannot change injection system without changing the technical homologation card of the engine, ‘ergo’ of the car.
    And what happens to emissions levels? I’m not sure that my car still fulfills Euro 5 rules.

    To know more about ‘happy Om 651 people’ around the world, U can also check out some of the following car blogs:

    Viel Vergnügen!

  4. Tirefriar says:

    In the late 90’s, Jaguar was tauting their Nikasil lined motors in XJ and XK 8 cylinder cars. Due to high sulfur levels in the US gas, Nikasil liners cracked resulting in loss of compression and effectively destroying the motors.

    Jaguar was aware of the problem but never ever publicly acknowledged it. It just went about quietly replacing failed engines for as long as the cars were under warranty. As soon as the warranty expired, the owner was out of luck.

    Jaguar did not announce an official recall because a)not all engines failed and b) they could be responsible for the failed motors that were out of warranty. Officially announcing such a catastrophic engine failure would have devastated a car company already infamous for questionable mechanical reliability. This was taking place around the time Ford set a goal for Jaguar to achieve JD Power and Associate #1 ranking.

    The same train of thought can be applied to MB in this situation. Not all cars are experiencing issues and MB will most likely wash their hands of the cars whose warranties expire. This is strictly a financial move, as MB can easily overcome this mechanical setback using their pretty solid reputation.

    In US there is what’s called a “Lemon Law” meaning a vehicle that has significant quality issues. If the problem has been brought up to the attention of National Highway Traffic Safety Administration, they can issue a recall on vehicles. The recall can range from minor repairs to major component replacements. Most recalls do not get national attention, but the recent one with Toyota’s “sticky accelerators” did. Toyota handled it quickly and properly. It cost Toyota over $2 billion. It affected the sales for just a brief moment but the swift action of the company and the openness with which it handled the issue restored consumer faith very quickly.

  5. maurizio sala says:

    As shown in the link here below, the ‘Frankfurter Allgemeine Zeitung’ informed that Mercedes-Benz has spent almost 500 milion of euro to repair the defective OM651 engines (only between 2008 and 2009).

    This authoritative german magazine calculated that 300.000 repairs were developed in the biennium all over the world. But failures and breakdowns continues even in 2013!

    Really a big problem in terms of money and … Customer Care for the Stuttgard brand!

  6. Lynnux says:

    Problems caused by injectors made by Delphi, a US Company. Yes, that’s the worst mistake Mercedes made: buy parts “Made in US” :-p

  7. maurizio sala says:

    Hey Linnux!

    Thanks for your contribution: this is your opinion.

    But you should know that Delphi – many, many years ago – announced to the press/customers the problem with these M-B injectors.

    Taking up its own responsibility.

    I do not seem they have done the same at the Aftersales/CS Offices in M-B, denying any problem.

    It is a matter of transparency.

    But – fortunately – Clients and the Web … do not sleep!


    I overhaul 651 engine 2 time. Replace oil pump also.but in 50 to 60 km.its locked crank bearing.its not happen with me in any other engine or brand.

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