If you own a Mercedes with a BlueTEC diesel engine, you may have heard quite a bit about the oil cooler leaks that have plagued some models. It is in fact quite a common issue with many of the BlueTEC diesel Mercedes. If like many of the owners out there, you are probably left with a lot of questions and wondering things like, “Which BlueTEC engines have oil cooler leaks?”, and “What are the signs of a leaking oil cooler?” That’s where the Atlantic Motorcar Center comes in. You see, we’re professionals in Mercedes service, after 33 years, we know these cars, inside and out. So we can clear up that confusion for you in this no-nonsense, straightforward post that you can reference. First, let’s cover a little basic information about what’s going on.
Let me first state that these engines are excellent in design (aside from the cooler seals), are very, very durable, produce excellent power, and are one of the best diesel engines we service. Once the oil cooler seals are updated, you’ll enjoy a very long life from the engine. So don’t be discouraged, or avoid, just be aware during purchase, and anticipate that this is not an “if” but rather a “when” repair.
As we mentioned above, engine oil cooler leaks are a common issue with certain Mercedes BlueTEC diesel cars. Specifically, the Mercedes “3.0 liter V6 diesel” engines, designated with the engine code “OM642”, also known as the “642 diesel”. These engines are used in a wide range of models over several years. Mercedes has issued a “TSB”, or “technical service bulletin”, relating to this exact issue and the proper repair procedure to correct it. Over the years, we’ve noted that an inordinate amount of 642 engines developed leaks from the oil cooler seals. On disassembly, we noted that these seals had degraded prematurely due the significant amount of heat they are exposed to. The oil cooler itself is positioned in the center of the “V” of the engine (see photos), towards the back of the engine compartment. As all engines, both gasoline and diesel, create heat while running, but the Diesel engines, due to the high compression radio, and the unique way these engines operate, they create a LOT of heat. The location of the oil cooler’s thermally insulated location on the engine under intake plumbing and so forth, prevents easy air cooling and heat exchange, and the original oil cooler seals simply fail prematurely.
The source of the oil leak is all too often misdiagnosed in workshops that are not famualr wth Mercedes, and needlesss parts are replaced, without correction or resolution of the oroigoanl problem. So when these services or maintenance tasks are being done at a shop that doesn’t specialize in Mercedes Benz repair, it is very common for the technician or do-it-yourselfer to incorrectly identify the source as a leaky rear main seal (which typically presents in an apparently similar way), leading to costly and unnecessary repairs that don’t solve the problem. As as experienced Mercedes specialist shop we immediately recognize the true culprit, or at the very least know to check the oil cooler for leaks prior to making any recommendations to the customer, potentially saving you thousands of dollars.
So what is the fix for keeping those oil leaks from reappearing as quickly as they occurred the first time? If the problem is seals that can’t stand the heat that they are exposed to everyday, is there any point to replacing them for another inadequate set of seals? Fortunately, Mercedes-Benz solved the issue in 2010 by updating those parts and now the only approved, effective solution is to replace those old seals with the new ones, made of an entirely different material called “Viton” rubber that is far better suited to the application, resists heat degradation better than the original rubber, and last far longer than the original seals. You can see the two parts in the image below, comparing an old, red/orange rubber seal with the new, superior Viton rubber seals which are purple. It is these purple seals that Mercedes adopted and are now the factory standard part.
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At Atlantic Motorcar we’ve developed some very specific procedures and tooling, combined with our expect technicians, to make this otherwise onerous repair a snap. Well, maybe not a “snap”, hard to call a day + of labor a snap, let’s just say that we make it flow very, very smoothly. And we warranty every repair for 2 Years, Nationwide, double the warranty of most new car dealers.
Not a simple repair, yes, but one, if done correctly, will last several years. That’s our goal with Mercedes, and other autos here, fix it right the first time, and prevent problems from happening in the first place. 30 years of service experience have well taught us that “an ounce of prevention is worth a pound of cure.” Be cured, once and for all, and give us a call, we’re happy to answer any service questions you might have on your Audi, BMW, Infiniti, Mercedes, Lexus, Volvo or Volkswagen.
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Questions, or if we can be of help in any way with service on your Audi, BMW, Mercedes, Mini Cooper or other European (and now Japanese) import, please contact us. Our team of Service Specialists are here to help, for even the newest autos! (207) 882-9969.
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The Atlantic Motorcar Center Service Team