Special notice: This will be the last update to this article before I take my entire website down in November 2024. I simply no longer have the time to help individuals like I used to and Mercedes has increased the price for access to their technical data to $7,000 per year, making it financially impractical to maintain my subscription.
I hope I’ve been helpful to the countless owners who’ve called me from all over the world during the 14 years I’ve been writing this Blog. It’s been quite an enjoyable experience talking with all of them. Their patronage has allowed me to establish college funds for my 2 grandchildren, and for that I’m most grateful. I also hope that the many readers of this Blog have also gotten a bit of clarity and direction for resolving their BlueTec problems.
August 19, 2024 – The views and opinions shared in this blog are strictly my own. They do not reflect or represent the policies, viewpoints, or opinions of Mercedes-Benz Group AG, Mercedes-Benz USA, or their authorized dealers. This article is intended for educational purposes. The author has no relationship with Mercedes-Benz or any of its affiliates.
VW and Mercedes were caught misleading consumers about their “clean diesel” problems by the Environmental Protection Agency (EPA) and the Department of Justice (DOJ). Both companies finally admitted to diesel emissions fraud. VW decided diesel engines were too dirty and stopped building them. On the other hand, Mercedes decided to continue the fight with the EPA and the DOJ and there doesn’t seem to be an end to the recalls and the litigation. The result is confusion. Many Mercedes owners believe that the AEM recalls resolve and end the problems with their BlueTec diesels – it doesn’t!
After years of litigation, the EPA and European regulators continue charging Mercedes with diesel emissions violations. And now Cummings Diesel has also been charged with virtually the same emissions violations as Mercedes. Diesel manufacturers all know that the diesel engine’s days are numbered. Diesels are simply too dirty. Diesel emissions systems are so complicated that they cost as much as the engine. And it gets worse every year.
There are legal ways to make the BlueTec work properly. I was helping owners solve these problems. But over time it keeps getting harder for individual owners to make the repairs themselves. And even though the repairs are legal, it’s virtually impossible to find professional help making the repairs. I no longer have the time to help individuals. I’ll leave my website up until it’s time to renew the hosting subscription in November of 2024.
After billions in fines and recalls, the EPA and DOJ haven’t helped owners nearly as much as they could have. The EPA and DOJ continue to confuse diesel owners when they over-simplify the problem. They accuse diesel manufacturers of installing a defeat device. There is no defeat device. Mercedes and other diesel manufacturers cut corners when they designed the engine and emissions systems. The EPA approved these “clean diesel” designs over 20 years ago. Engineers at the time knew their designs couldn’t live up to the hype of “clean diesels”. Engineers knew these “clean diesels” would require significantly higher maintenance than older diesels.
The defeat device the EPA is talking about is nothing more than software programming that’s trying to compensate for the cost-cutting designs from 20 years ago. Mercedes and other diesel manufacturers are trying to make their outdated designs meet the current NOx and soot emissions. Mercedes and the EPA know precisely what’s wrong with the BlueTec and how to fix it. But Mercedes doesn’t want to spend the money and the EPA doesn’t want these dirty diesels hanging around for another 30 years. The result is exactly the mess we have today, and of course, the consumer is always left holding the bag. For consumers, this isn’t just about protecting their financial investment, it’s also a real safety issue. How can anyone design a diesel emissions system where you have to keep one eye on the DPF monitor and the other on the road? How is this any different from texting while driving?
When I started this article 14 years ago, I was simply trying to explain the BlueTec to my local customers. I didn’t realize that nobody else was saying anything about BlueTec’s technical problems. But it wasn’t long before I was getting phone calls and emails from owners around the world sharing their problems and asking for advice. At first, it seemed like the problems were oil-related. The Mercedes recommended oil was breaking down from the extreme heat caused by DPF regenerations.
The DPF captures and stores the soot in diesel exhaust. After a predetermined time, the engine’s computer increases the exhaust heat and the DPF incinerates the soot it has stored. Even now, Mercedes hides many of the technical details about the DPF regeneration cycle. Mercedes still claims this is proprietary information and doesn’t even share most of it with their dealers. Mercedes also changes their proprietary DPF regeneration process. Mercedes is currently making a major change in the regeneration operating parameters. BlueTecs have so much trouble with the DPF clogging, that Mercedes created software updates to increase the frequency of the regeneration. When Mercedes makes these changes, they only share small bits and pieces of the process with dealerships or owners. At the heart of practically every BlueTec problem is the tremendous heat required for the DPF regeneration.
Once you understand how all of these problems are related, it makes sense. Today you’ll find lots of people who think they know something about the BlueTec. Most are 10 years behind the curve. They’re still stuck on the oil and the parts that fail from oil sludge. They can’t move past the symptoms and see the actual problem. The first thing they tell owners is to use the Mercedes MB229.52 specification factory-recommended oil. The BlueTec oil topic is so old I can’t believe I still get questions. Mercedes is swamped with EGR valve and DPF failures. These parts are on constant months-long backorder! If the MB229.52 oil is so great, why are these parts full of oil sludge? Anyone telling you to use the MB229.52 oil doesn’t know anything about a BlueTec. Even Mercedes has given up on their oil. Read the Legal Notice on their recommended oil website.
Any oil with the MB229.52 or MB229.51 approval is designed to theoretically protect a new emissions system. Everything changes when the engine gets to higher mileage. The oil breaks down and sludge clogs the EGR, EGR Cooler, Intake Manifolds, and the DPF. In a new engine test to certify the emissions system, the oil complies with the EPA regulations. But over time, these emissions protection oils clog the engine with sludge.
If Mercedes doesn’t even believe in their oil, what is the right oil? There isn’t one oil that works in every possible BlueTec driving situation. Some oils work better for short trips in cold weather. Another oil works better when towing a trailer in 100F Summer heat. Some owners drive 5,000 miles a year while others drive 30,000 miles a year. Some oils are better for new engines, and some are better for high mileage. None of the Mercedes oils are approved for B20 biodiesel fuel. I’ve only found one oil approved for B20 biodiesel.
When people ask me what’s the best oil, I tell them it depends on many variables. I can’t say this often enough; oil is only one small piece of the BlueTec puzzle. The very best oil for your specific type of driving won’t solve or prevent all of the problems. Better oil and better oil filtration are extremely important, but they can’t fix years of neglect. Generally speaking, a very good oil for the average BlueTec in Winter driving is Red Line 5W/40 Euro-Series Diesel oil. For Summer driving, Red Line 15W/40 Diesel oil is an excellent choice. Red Line is ester synthetic oil and it’s far superior to petroleum-based oils. But this doesn’t mean these 2 examples are the absolute best for you. There may be better oil choices for your specific situation. And forget about changing your oil every 20K miles because doing that will clog your DPF faster than anything. 5,000-mile oil changes are critical! Or you can spend hours yelling at your Service Advisor over repeated failures.
The problem with the AEM recall is that none of the new parts fix what causes the BlueTec problems. The new parts only address the symptoms of the flawed BlueTec design. These “updated” parts will also fail as soon as they’re clogged with oil sludge or subjected to extreme heat from the DPF regeneration.
To improve reliability and reduce your maintenance cost, you have to reduce the frequency of DPF regenerations. For Mercedes to legitimately reduce the frequency of regenerations, they would have to redesign the OM642. The party is over. Mercedes is not going to redesign the engine. They’re also not going to tell consumers how they can work around design problems. Successfully owning a BlueTec diesel means that owners must educate themselves about how the BlueTec operates and be willing to step up the preventive maintenance. If Mercedes and other diesel manufacturers told buyers how complicated the diesel emissions system is, the diesel market would disappear. I know 99% of BlueTec owners will never make the effort to do what it takes to own a trouble-free BlueTec. Modern diesels are far too complicated for most owners.
I mentioned Mercedes proprietary DPF regeneration process. Why does the owner need to understand the process? Mercedes tells dealers and owners the DPF regression is automatic. Mercedes implies that owners can drive a BlueTec just like a gasoline engine. Since you’re reading this, I suspect you know this is not true. You also can’t get an explanation from your dealer because Mercedes has also kept them in the dark. While you’re BlueTec is under warranty, Mercedes will keep throwing parts at the problems. It’s an inconvenience now, but you know the party will come to an end one day. Most new owners quickly sell their BlueTec when they have to pay for these repairs. I then get calls from the second owners and I get to explain what’s happened.
It’s taken me years to figure out the technical details of the DPF regeneration. Mercedes finally came to realize the regeneration operating parameters where too complicated. Too many DPFs were clogging and causing the engine to suddenly stop running. Mercedes has quietly changed the DPF operating parameters. To keep the DPF from clogging, they’re now programming it to regenerate more frequently. If you have the latest DPF software update, you can let your engine idle in your driveway and the DPF will regenerate. In the past, the vehicle had to be moving for the DPF to regenerate. The DPF gets so hot, there must be enough air moving across the DPF to cool it down. Instead of regenerating every 300 to 600 miles, the DPF will now regenerate every 180 to 200 miles. These are only a few of the recent changes, there’s many more. The takeaway is that the DPF will be running much hotter. That extreme heat is funneled back into the engine via the exhaust-driven Turbocharger. The result will be more preventive maintenance or more heat-related failures. There’s no easy way to know which DPF programming you have. Sooner or later, Mercedes will offer you a free software update for something and that’s when they’ll also download the more aggressive DPF regeneration.
My gripe with Mercedes is they don’t explain this or any of the extra maintenance required to actually keep a BlueTec running with the fewest problems. Mercedes sends letters to owners after their AEM recall work is completed telling them they can go 20,000 miles between oil changes – that’s horrible advice! There’s no mechanism for owners to get a forthright and honest explanation about how to properly maintain a BlueTec. The ridiculous cost of Mercedes routine service is a waste! It’s not a matter of spending more money. The problem is there’s no incentive for dealers to help owners prevent problems. If you haven’t noticed, service appointments at dealerships are backed up for months leaving owners in limbo. EGR valves and DPFs have been on backorder for months. Do you think your dealer has the time or would ever explain how installing an aftermarket DPF monitor, Catch Tank, or better oil filter can save you thousands in preventable repairs? Why would they? They’re in the business of fixing broken diesels.
The DPF regeneration heat is only one of BlueTec’s several problems. As I’ve said, the DPF regeneration heat causes a cascade of other problems. The EGR valve fails, but nobody explains what caused it to fail. Replacing the EGR valve is only a temporary fix. When the engine oil cooler leaks, nobody explains that it’s caused when the oil seals become brittle because they get so hot. The engine oil gets so hot that excess crankcase pressure pushes oil past the piston ring seals. Understanding the root cause of all these problems and reducing the heat from the DPF will impact all of these problems. Waiting until you see these problems is too late. There’s way too much to explain here. I’ve barely touched on the DPF regeneration complexities.
I’m retired after over 50 years with Mercedes-Benz as a Mechanic, Shop Foreman, Training Instructor, Service Manager, Independent Shop owner, recipient of five Star Technician Awards from Mercedes, and 6 years as President of the Mercedes-Benz Parts and Service Managers Guild.
There are legal ways to make the BlueTec work properly. I was helping owners solve these problems. But over time it keeps getting harder for individual owners to make the repairs themselves. And even though the repairs are legal, it’s virtually impossible to find professional help making the repairs. Unfortunately, I no longer have the time to help individuals. I’ll leave my website up until it’s time to renew the hosting subscription in November of 2024.
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Over the years I continued adding short bits of specific BlueTec technical information to the bottom pages of this article. These things are important but they’re beginning to pile up. I haven’t had time to update them and I hate to delete them. One day I’ll figure out what to do with them.
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This section is about technical stuff. It’s important, but not every BlueTec is affected.
BlueTec OM642 problems typically fall into two general areas:
Area One is about mechanical problems resulting from Mercedes cost-cutting shortcuts when they designed the engine. This is what’s gotten Mercedes and customers into so much trouble with the EPA. The EPA and automotive articles like to lump all of this into what they call a defeat device. The problem is not some device, it’s a group of design shortcuts. Before the first OM642 rolled off the assembly line, Mercedes knew these engines would eventually blow up in their face. Some of the shortcuts aren’t so obvious, so I thought I should list them.
1. No Break-in oil in the new engine. Not all new engines have perfect piston ring clearances Think of the Bell Curve of averages. A few engines have perfect piston ring clearances, most fall someplace in the middle of the Bell Curve, and a few have terrible piston ring clearances. Break-in oil allows the not-so-perfect piston rings to form a tight seal against the cylinder walls. This is one of the main reasons some owners say they don’t have problems, and others have lots of problems.
2. Only one PCV valve. The engine should have two.
3. Mercedes didn’t water cool the Turbocharger, Intercooler, or Exhaust Manifolds. This saves a lot of money, but makes it very hard to control the NOx emissions.
4. Post Injection. Mercedes saved a lot of money by not including the hardware to inject raw diesel fuel into the DPF for the regeneration.
5. No DPF monitor.
I have so many owners tell me their problems seemed to start all at once. They don’t realize these problems accumulate and once you notice them, they’re deeply entrenched and much harder to resolve.
Area Two is about the electrical system problems. Specifically, intermittent low voltage in the CAN bus network which transfers data between the multiple computers. By now most owners are familiar with Mercedes endless software updates. Intermittent low voltage in the CAN bus is the actual problem and not software that needs updating. Mercedes doesn’t want to own up to the real problem, so they keep blaming software. Yes, software can be a problem, but the most of the problems are from intermittent low voltage in the CAN bus.
If you drill deep enough, virtually every problem falls into one or both of these areas. Mercedes addresses most of these problems in their technical publications. They just don’t make it easy to find or understand. There are ways to avoid practically all of the problems, but no dealer and most independent mechanics won’t take the time to explain how to avoid the problems. Owners don’t realize the complete cost of repairing. There might be an easier way or it should be a warranty repair. Often there’s more to the repair that’s being ignored because it’s low profit or hard to do. Dealers aren’t in the prevention business. They’re in the Sales and Repair business.
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Here below are the most common and current problems. They’re in no particular order. I’ve taken a couple of the most important problems and gone into more detail. I’ve done this to give you some idea of how complicated these problems are. Even this extra detail doesn’t come close to thoroughly explaining the problem. Other problems I’ll give a brief explanation. This is by no means every problem. Some owners have very few problems.
There are technical reasons why some owners don’t have these problems. Sometimes it’s dumb luck. Other times it’s because someone knew what they were doing. Luck is not a very reliable strategy for owning a BlueTec.Many of these BlueTec problems have been around so long I tend to assume people already know about them. New problems keep coming up and it takes time to figure them out. If you have an older BlueTec I still have all that information. I had to omit some of it to make room for all of the newer problems.
Break-in oil for the new OM654 diesel.
The new OM654 diesel does not come with Break-in oil. When the engine is new, the factory oil needs to be drained immediately and special diesel Break-in oil needs to be used for the engine’s first 1,000 miles. The original oil filter also needs to be changed out for a brand new one when you refill using Break-in oil. The OM654 also needs a traditional dipstick installed. The oil level is very hard to check using the instrument cluster display. Don’t let your dealer tell you there isn’t a dipstick. It only costs $25 and is easy to install.
The engine intermittently dies. Intermittently surges while driving on flat roads or up hills. Intermittently stumbles accelerating from a stop light. Intermittent rough idle. Poor fuel mileage.
All of these can be caused by several different things. They all feel the same, but the fault codes are different…. most of the time. These engine performance problems can be caused by:
1. Intermittent low fuel rail pressure. The High-Pressure Fuel Pump can be damaged by gasoline or water in the fuel. Fuel contamination. The fuel pressure from the high-pressure pump intermittently drops resulting in tiny metal flakes going into the fuel rails and injectors. Any fuel system fault code should be first diagnosed by cutting open the fuel filter and inspecting for tiny metal flakes. If metal is found in the fuel filter, the entire fuel system must be replaced. This is a $15,000 to $17,000 repair. There are ways to prevent this from happening. Look for fault codes like P0087 and P0088. Also, any misfire or injector fault codes.
2. The EGR valve and/or the EGR By-pass valve may intermittently stick. This is caused by excessive blow-by from the PCV valve. Oil misting coats the EGR and air intake system. The oil mist hardens into thick carbon deposits. The EGR valve must be replaced or cleaned. The EGR / air intake system must be cleaned or replaced. Mercedes will pay for this as part of the AEM recall. BlueTec diesels not covered by the AEM have the same problem. The owner must pay for these repairs. A Catch Tank and better oil prevent carbon deposits. Look for EGR fault codes like P24A5.
3. If the DPF is starting to clog, you’ll get these same symptoms. You’ll see fault codes for Turbocharger low boost pressure. The Turbocharger is exhaust-driven. Exhaust gases can’t flow properly to the Turbocharger when the DPF starts to clog. Many mechanics misdiagnose this as a bad Turbocharger. First, check the soot and ash levels in the DPF. High oil consumption will clog the DPF and give you fault codes for the Turbocharger. It’s not the Turbocharger, but it will feel just like the EGR or low fuel pressure. You can often just look at the impeller for the Turbo and see any damage. You can also tap on the exhaust manifolds with a rubber hammer. If you hear a metallic rattle, the exhaust manifolds are breaking up and damaging the Turbocharger.
4. Intermittent low voltage in the CAN data network can also cause the same performance problems. If you have the Mercedes auxiliary battery for BlueTec Sprinters, it’s not likely you’ll have these problems. Check for numerous low-voltage diagnostic fault codes.
5. Check for a loose ground strap from the engine to the frame. This simple thing can also cause the same performance problems. The ground strap doesn’t have a fault code. But it causes other fault codes that don’t make sense.
To avoid wasting money diagnosing these performance problems, you must have a method. Too many mechanics get lost and start throwing parts at the problem. Do the easy stuff first. Check the ground strap. If you have fuel system fault codes, cut open the fuel filter. Even if that’s not the problem, normally the fuel filter is close to its normal service interval. You didn’t really waste any money replacing the fuel filter. If the vehicle has other maintenance problems, do the fuel filter first. If it has metal inside, the repair cost is a major problem. Now you can decide if you want to spend money fixing the other problems. If the mechanic fixes a bunch of other stuff first and then you find metal in the fuel filter, you’re trapped.
If you find EGR fault codes, open the EGR valve and see how dirty it is. If it’s caked in black carbon crud, the rest of the EGR and air intake system is also full of the same crud. Replacing or cleaning the EGR valve may seem like it runs ok, but it will soon have more trouble. When you’re spending lots of money on these repairs on a high mileage engine, you need to be aware of all the other possibilities. This is how owners get upside down in these BlueTec diesels.
If your engine is burning oil or the timing chain is rattling, you need to step back and think about the total cost. You might be better off replacing the engine or selling the vehicle and putting your money towards a better vehicle.
Most Service Departments are not good at helping you make the best repair decisions based on what typically happens to a vehicle like yours. You need to be aware of the potential problems. You also shouldn’t assume the worst. The AEM recalls make fixing those models more reasonable. There are more AEM recalls coming and dealers are not allowed to explain them until they’re announced.
Intermittent no start, dead battery, odd electrical problems: (2019, 2020, and 2021 – 907 Sprinter.) Electrical problems are getting to be a big problem.
Service bulletin LI22.10-N-071666: The left motor mount bolt breaks or the ground cable works loose. The engine can intermittently lose its ground connection to the frame. This can be very difficult to find. This happens more often in vehicles driven on rough roads. The simplest thing is to run a separate second ground cable from the engine to the frame. It doesn’t cost anything and it’s one less thing to cause a problem.
LI54.21-N-069524 is about condensation dripping into the Electronic Ignition Switch (EIS). This causes the same intermittent no-start and other electrical problems. The preventive fix is simple. Mercedes will not pay for the expensive parts damaged by condensation.
LI54.30-N-071191 is about intermittent low CAN data system voltage causing the transmission to stick in Park. This is also the same reason the 907 transmissions intermittently pop out of Park and the Van rolls away.
LI91.60-N069828 is about intermittent SRS warning lights after electrical work such as removing the driver’s seat to access the Main starter battery. You might unplug the SRS 50 times and nothing happens. One time the SRS didn’t like it, and now you have an SRS failure.
LI27.60-N-071845 is another bulletin about intermittent low voltage in the CAN data network that also causes the transmission to stick in PARK. Like the previous bulletins, low CAN data voltage causes the transmission to pop out of PARK.
LI54.71-N-072095 is another intermittent no start or the engine won’t shut off.
LI82.20-N-071665 is another intermittent no-start caused by moisture in the electrical system.
LI14.40-N-072089 is the latest in 20 or 30 bulletins about intermittent low voltage in the AdBlue system.
Mercedes doesn’t explain the common factor in all of these bulletins. Mercedes knows what’s causing all of these 907 Sprinter electrical issues, but they don’t want to pay for it. Mercedes also doesn’t tell you that each one of these problems can leave you stranded. Mercedes also exacerbates this problem by scattering the information across different locations in their Workshop Information System.
Readiness Monitors / Failed Smog Test 907 Sprinters: MB is having trouble with the 907 Sprinter failing the Smog Test because the Readiness Monitors won’t reset. When this happens, the engine still runs normally with no CEL. MB knows what the problem is, but they say they don’t know. It would trigger a very expensive recall. The problem is with some Sprinter vans that don’t have the auxiliary battery. Intermittent low voltage in the CAN bus interrupts the Readiness Monitors. Installing the factory auxiliary battery and the 280Ah high output alternator will solve the problem. You can also try trickle charging the battery every night and keep the Main battery fully charged until the monitors are complete. You may have to replace the Main battery with a genuine MB 92Ah AGM battery. NEVER use a lead acid battery.
DPF Failure – Diesel Particulate Filter (DPF) working parameters:
(Go to the Sprinter Owners Forum and do a search for “DPF Failure”. This will give you some idea of how prevalent DPF failures really are.)
Why do so many DPFs fail? As you read through the complaints, you’ll notice nobody explains exactly what causes the DPF to fail. DPFs fail from extreme heat. The DPF gets so hot, so many times, the internal core crumbles apart and then looks like something you’d scoop out of your fireplace.
Mercedes went cheap and didn’t water cool the Turbocharger, Intercooler, or the exhaust manifolds. They need to be water cooled to effectively control the combustion and exhaust temperatures. Without water cooling, the only way they have to cool the combustion and exhaust temperature is to mix in slightly cooler gases from the EGR valve. The problem with EGR gases is they’re loaded with exhaust soot. The DPF is already dealing with exhaust soot, and now Mercedes mixes even more soot from the EGR valve.
But the problem doesn’t end there. Mercedes also went cheap and only put one PCV valve on the OM642. It needs two PCV valves. Having only one PCV valve causes lots of hot oil vapor to mix into the EGR gases. Now you have excessive soot mixed with oil vapor going into the DPF. Once you understand how the emissions system works, it becomes obvious and inevitable that the DPF and the rest of the emissions system will have constant failures.
Some people drive in the ideal climate and the ideal distance. They love to brag on the Sprinter Forum that they don’t have any problems. I’ll never understand the point. It’s like going on your refrigerator forum and bragging that your refrigerator light always comes on when you open the door. Those braggers aren’t much help when you’re standing at the Cashier’s Counter staring at another stomach-churning $1,000 oil change with an oil that’s already ruining your DPF and emissions system.
When people drive 10K to 20K miles between oil changes, the oil vapor gets filled with soot. The DPF has to work extra hard to burn off this mess. Keep the crud out of the DPF, and it doesn’t get so hot. When the DPF is constantly running at 1,600F, it rips everything else apart. The DPF temperature sensor cost almost $1,000 and it also gets cooked right along with the NOx sensors, EGR diverter valves, and Back Pressure sensors. These parts can only take so many extreme heat cycles before they fail. This isn’t a mystery. This oil sludge is continuously building up inside the engine and finally reaches the point where you’re constantly seeing the Check Engine Light and the Limp Home lack of power. It’s way more expensive to clean up the mess than it would have been to keep it clean from the beginning.
AEM recalls and the recalls of the recalls. I assume most people know roughly what the AEM recalls are about. Mercedes keeps extending the deadline. The AEM recalls are very important and you should get everything Mercedes offers.
The AEM recalls do not fix every problem. Dealers will not explain everything what’s actually needed. The fundamental problem of blow-by oil vapor clogging the air intake system still remains. Over time all the problems will return. The only way to prevent the AEM problems is to keep the air intake and EGR system clean. Blow-by oil vapor entering the air intake system is the root cause of all the AEM problems.
New engines can get a head start with Break-in oil in the new engine. Mercedes does not put Break-in oil in new engines. Some new engines get lucky and have tight piston ring clearances from the factory. Some engines are average. Some engines have terrible piston ring clearances. These later engines will have significant problems. (See service bulletin LI03.10-N-071148.) Some new engines will fail within a few thousand miles. There’s no way of knowing which engines will be perfect and which ones won’t. Using Break-in oil, installing a Catch Tank, and then using an Ester synthetic diesel oil prevents problems.
Some owners think their BlueTec doesn’t run as well as it did before the AEM work was done on their vehicles. Odds are intermittent low voltage is the culprit. When your mechanic does the AEM he should connect a special battery tender designed specifically to maintain the correct voltage for software updates. A battery charger is not designed for software updates. If your mechanic doesn’t follow the directions and the CAN data system voltage drops below 12.55 volts, the software will be corrupted. If you only have one battery and it’s not the original 92Ah AGM battery, or it’s sulfated, or it can’t pass the load test; you’ll have software data problems. The odds are your mechanic doesn’t even test your battery because Mercedes doesn’t want to create any more problems than they already have. Mercedes won’t pay for a new battery and the AEM customer doesn’t want to hear anything about buying a new battery or the auxiliary battery.
People think if their vehicle starts and runs, the battery is OK. Wrong!
Before your mechanic does anything, he should load-test your battery. The battery needs to deliver the deep discharge to constantly supply over 12.55 volts to the computer network. Mercedes offers the Sprinter with two big AGM heavy-duty batteries. But most Sprinters get ordered with one battery to save money. If you have a genuine Mercedes 92Ah AGM main chassis battery in good condition, it’s barely able to keep up with the electrical demands of a Sprinter.
If you thought the genuine Mercedes battery was too expensive and you replaced it with a cheaper battery, you’ll have problems you never imagined. The mechanic doing your AEM recall is not going to tell you anything about your cheap battery. The mechanic is going to do the AEM recall work and not waste his breath explaining the electrical system to someone who probably thinks he’s trying to gouge him for a new battery. Never mind trying to explain the auxiliary battery and intermittent low voltage corrupting the software data. Most customers don’t want to hear it.
Your Sprinter van may start normally. Parasitic draws in the electrical system or frequent short trips can easily weaken a good battery. The first thing your mechanic should do, before any diagnostic fault code repair, is load test your battery. Most owners think the mechanic is just trying to sell them stuff they don’t need. Most mechanics do what they’re told and give you back your van with the repairs you or Mercedes are willing to pay for. If you want it fixed right, you need to educate yourself about how all these systems work. If your mechanic suggests a Load Test on the electrical system, you’ve found a good mechanic who knows what he’s doing.
Sprinter electric sliding door: Sprinter electric sliding door malfunctions are common complaints. If you have an RV with the bathroom next to the sliding door, it can be very expensive to repair. If something happens to the door motor or wiring that requires access, the bathroom will have to be removed. That’s a huge job. In other words, do not buy a Sprinter RV with the bathroom next to the sliding door.
Fault Code P30034: The flow rate of the OM642 EGR position sensor is too high. (See Service Bulletin, LI14.20-N-073867) This code covers a wide range of common problems. A lack of power when cold. The transmission jerks when going into gear. Check Engine Light and Limp Home. It can be as simple as the air tube going to the turbocharger being loose, or there’s a leak in the exhaust. It’s often a sign the EGR valve, EGR By-pass valve, and/or the EGR Cooler are clogged with oil sludge. If that’s the case, what’s causing the oil sludge?
The OM642 PCV valves have been wearing out much faster than expected. Extended idling is one cause. Owners are reporting worn-out PCV valves after only 12,000 miles. Remove your old PCV valve and compare it with a new part. The rubber seal will be badly worn. It should be obvious. You can also look at the impeller of the turbocharger. If you see oil under the impeller, it’s coming from the PCV valve. Poor oil quality and excessive blow-by at the piston rings compound the problem. The DPF regenerates too frequently and overheats the NOx sensors causing them to fail. NOx sensors are currently on 6-month backorder. When replacing every pair of NOx sensors, you should also conduct a very close inspection of the PCV valve. You’re likely to find dozens of other fault codes with P30034. They’re all caused by oil vapor getting past the PCV valve and into the air intake system. Fault code P30034 is the start of a cascade of problems.
Fault Code P246309: The diagnostic system says the DPF is full of soot. If you see this fault code or any fault code about the DPF filled with soot, it means the PCV valve is worn out.
Amazon Sprinter Delivery Vans roll away after driver puts the transmission into PARK: (907 BlueTec Sprinter, model years 2019, 2020, 2021, and 2022).
You’ve probably heard about this widely publicized problem. YouTube has numerous videos of Amazon drivers chasing their Sprinters as they roll away. Mercedes has blamed drivers for the problem. The NHTSA has ordered Mercedes to implement their third recall for this one problem. 124,000 Sprinters will start receiving recall notices in December 2022.
Mercedes says a software update will fix the problem. Mercedes must have forgotten they already addressed this problem years ago. This transmission (722.9) has been used in passenger models for many years. Low voltage in the CAN data network can cause the transmission to intermittently stick in PARK or pop out of PARK. Mercedes service bulletins (LI27.60-N-071845) about low voltage to the transmission control module are correct.
The problem is the 722.9 transmission in slow-moving delivery Vans. There’s nothing wrong with the transmission. The 722.9 is a good transmission. Amazon or FedEx delivery vans are prone to low CAN data voltage because they drive slow speeds and short trips. With frequent restarting of the engine, the Main battery is always struggling with low voltage. Amazon also didn’t order the vans with the Mercedes auxiliary battery. If the CAN data voltage intermittently drops below 12.55 volts, the software data transfer gets corrupted. Mercedes also uses a small emergency battery to supply extra voltage to the PARK actuator in the transmission. But the emergency battery also gets low on voltage when the Main battery is not fully charged.
With the recall, Mercedes is trying to fix low voltage with software. Mercedes knows how to really fix the problem. As of 2023, Mercedes has replaced the emergency battery with a Super Capacitor. Mercedes also increased the 2023 alternator to 280 amps. The new alternator will recharge the Main battery much quicker at slow speeds.
Mercedes also offers the 907 Sprinter with a factory-installed 92Ah AGM heavy-duty auxiliary battery under the R/F seat. Apparently, Mercedes didn’t explain this to Amazon when they bought 40,000 Sprinters. In case you also didn’t order the auxiliary battery when new, Mercedes offers a much needed retro fitted auxiliary battery in the engine compartment. All of these things give the Sprinter additional voltage capacity for the entire CAN data network.
Low system voltage has been a problem for the entire CAN data system for many years. If you have a fully loaded RV with lots of electrical consumers, you absolutely need the auxiliary battery and the 280-amp alternator. For pre-2023 Sprinters, there’s a very good aftermarket 280-amp alternator that’s specifically designed to operate with Mercedes computers. If you have a 907 Sprinter with the factory auxiliary battery, you’ll not have a problem with rolling away or many other common problems.
The “No Start Countdown”: Another long running problem is with the Selective Catalytic Reduction, or SCR/AdBlue system. From 2009 right through 2022, Mercedes has put bandaids on the SCR system. I’ve lost count of all the software updates Mercedes claims will fix the SCR/AdBlue system.
Many SCR problems are caused by Mercedes cheap oil, while others are caused by low system voltage. Over time, the factory-recommended oil vaporizes so easily it causes the DPF to regenerate too often. That creates extreme heat in the exhaust system. High exhaust temperatures from stop-and-go heavy traffic combined with frequent DPF regenerations causes the NOx sensors to overheat and fail. Amazon and FedEx can tell you how often this happens. This is also what causes the EGR valves to fail. Extreme exhaust temperatures either clog the EGR valve or burn out the EGR electronics. EGR valves are a frequent complaint and are on endless backorder. If the EGR clogs it can be cleaned. If the electronics fail the EGR valve must be replaced.
Better engine oil keeps the EGR clean and doesn’t clog the DPF. But as soon as you say something about better oil, everyone thinks better oil will save the day. Better oil certainly helps, but it’s just one piece of the puzzle.
Like most of the other BlueTec issues, Mercedes doesn’t explain their BlueTec diesel oil. Mercedes likes to scare owners with dire consequences if they don’t use the Mercedes oil. The oil industry doesn’t help either. People don’t have time to study complicated oil standards and specifications. People give up and use the Mercedes oil, not knowing the Mercedes oil only has the minimum standard. Nobody explains the upper end of the oil quality. The AEM recalls finally forced Mercedes to publish the technical data for their BlueTec oil.
Mercedes recommended BlueTec oil is not synthetic. The API and the ACEA don’t approve the Mercedes oil for diesel engines. If you know where to look, Mercedes even admits it. The Mercedes diesel oil is API Group 1 conventional mineral oil. API Group 5 is the highest quality. This is not my opinion. Mercedes own documents admit their oil is Mineral Oil. It’s not synthetic, nor is it approved for diesel engines by the API or ACEA. It doesn’t meet the warranty requirements Mercedes imposed on other oil manufacturers. The Mercedes diesel engine oil is a fuel-efficient oil designed for gas engines.
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The API (American Petroleum Institute) categorizes motor oil into 5 different quality groups. I included this section for owners who want more technical information about determining the actual quality of any motor oil. These 5 groupings spell out the quality differences between every type of oil. Group 1 is the lowest quality and Group 5 is the highest quality. Unfortunately, most oil companies don’t clearly state which group their oil belongs to. Let’s say you really want to know the API quality group for your favorite oil. On the oil’s website, they’ll publish your oil’s SDS (Safety Data Sheet). Look at Section 3 on the SDS. Compare the specific verbiage to the following API group descriptions. That will give you the actual API Group number.
Oil companies and auto manufacturers intentionally make all of this very confusing. As with most things, their motive is more money. There’s a lot more profit selling cheap oil with fancy packaging. Even if you ultimately discover the oil damaged your engine and its emissions system, what are you going to do about it? Over the years Mercedes has lost many Class Action lawsuits about engine failures caused by their low-quality oil. Yet they continue with the same pattern and practice. But it’s not just Mercedes, oil companies make a lot more money off a Group I oil than a Group V oil. It’s like buying wine based on what the label looks like. Can you imagine what would happen if oil companies had to put the API group number on the oil label and explain the difference? Just labeling the lowest quality oil as Group 1, tells you a lot.
API Group I
Group I base oils are the least refined base oils. Group I is defined as a “highly refined mineral oil”. These are generally used for less demanding applications and are not a good lubricant for modern engines. Mercedes factory recommended oil is API Group I. You can look it up on Mercedes own Safety Data Sheet. Mercedes factory recommended oil is API Group I.
API Group II
Group II oils have average performance in volatility, oxidation stability, wear prevention, flash point, and they have fair performance in cold temperature environments. Group II lubricants are most commonly used as conventional lubricants where synthetic oils are not required.
Group II base oils undergo hydro-cracking which is a more complicated process than the process for Group I oils. Hydro-cracking is a process that breaks down large hydrocarbon molecules into smaller ones. The hydrocarbon molecules of these oils are saturated, giving them better anti-oxidation properties. Group II oils are priced closely to Group I oils.
API Group III
Group III base oils are “severely hydro-cracked”, hydro-isomerized, and hydro-treated to crate the best grade of “petroleum” base oil. These products offer superior stability and molecular uniformity, which makes them ideal for some semi-synthetic lubricants.
Some people consider Group III base oils to be synthetic. The API classifies them as mineral oil since they are derived from crude oil. They do mimic characteristics of synthetic oils including high viscosity indices. A lawsuit between Mobil and Castrol occurred due to Castrol marketing their Syntec lubricant as a synthetic even though it was composed of Group III base oils. In a 1999 Supreme Court ruling, the product was allowed to be marketed as a synthetic. Over the years this has caused consumers a great deal of confusion regarding synthetic oil. Courts have ruled the word “synthetic” is a marketing term. The word has no scientific meaning. It means whatever the Marketer thinks it should mean. Yeah, it’s just one more sketchy detail the oil industry would rather not explain. Germany and Japan rejected the Supreme Court’s decision. Only API Group IV and Group V oils can legally say they are “synthetic” oils.
API Group IV
Group IV base oils are polyalphaolefins (PAO). Group IV are synthetic oils. These are not extracted from mineral oil but made from small uniform molecules. This is also the biggest advantage of PAOs. They can be completely tailored to have a structure with predictable properties. The uniformity and manufacturing of these oils allow for predictable properties that assure performance in tough conditions. These properties include extreme temperature stability, which makes these products ideal for cold and hot weather climates. If you look at the Safety Data Sheet, you’ll see a bunch of long chemical names. You should also see “PAO” or “PAG”. These are excellent synthetic oils.
API Group V
Group V oils are man-made chemicals. Group V are also synthetic oils. They include, among others, naphthenic oils and esters. Usually, Group V oils are not used as a base oil but as an additive to other base oils. Chemical Engineers use these expensive chemical building blocks to construct lubricants for Jet engines and other extreme operating conditions. Mercedes dealers in Europe use Group V ester synthetic oils in their BlueTec diesels. The Safety Data Sheet will say this is a Synthetic Lubricant.
It’s really hard for owners to believe Mercedes would not use synthetic diesel oil. I want owners to verify for themselves what they’re using in their engines. Mercedes finally has a website where consumers can look up the SDS (Safety Data Sheet) for their oils. Google Mercedes SDS and it will lead you to the website.
Deciphering the coded language in the SDS is the only way consumers can get close to a truthful answer. When you find the SDS, look for section 3. You should see the word “composition”.
If your oil says it’s a highly refined “mineral” or “petroleum”, it’s an API group I non-synthetic oil. Sometimes the manufacturer says it has “additives”. Every oil has additives. It’s the words “mineral” or “petroleum” that you don’t want to see. That’s the lowest quality on the market. It doesn’t matter what adjectives they use to make it sound more exciting, it’s the lowest quality oil. If they won’t show you the SDS, it’s safe to bet it’s Group I mineral oil. If they say the information is “proprietary”, it’s not good oil. If the oil company is selling a good oil; they’ll tell you what’s in it.
If it says the oil is “severely hydrocracked mineral oil”, it’s API Group II.
If you see “distillates”, “hydrogenated base oil” or “hydrotreated heavy paraffinic”, it’s a Group III synthetic blend. This is the most common oil you’ll see advertised. The problem is, you have no way of knowing the quality of the chemicals in the oil. That’s what makes up the quality of a Group III oil. Depending on the quality of the chemicals, some Group III are very good oils. But it’s also the reason Europe and Japan won’t allow Group III oils to say they’re “synthetic”.
If you see “formulation is considered a trade secret and specific chemical identity and exact percentage (concentration) of composition may have been withheld. Specific chemical identity and exact percentage composition will be provided to health professionals.” This means the oil isn’t what the oil company is advertising. If it was, they would tell consumers. This was copied from the Mobil One 5W/30 ESP SDS Sheet.
Group IV oils don’t have any of the Group II or III wording. Group IV oils have long chemical names in the SDS. You should also see “PAO” or “PAG” in the description. Group IV are excellent oils. They’ll normally say “full synthetic” on their label. Group V oils also say “full synthetic” and that’s confusing.
Any oil approved for BlueTec diesels should say API “CK-4” or ACEA “C3” or “E11”. They may also say API “CF”. They might say MB229.52, MB229.51, MB228.52 or MB228.52. But that’s only if they’ve paid Mercedes for their copyright. ExxonMobil admits their Mobil One 5W/30 ESP has never been submitted to the API or ACEA for diesel testing. It’s ExxonMobil’s opinion their 5W/30 ESP oil meets the API SM/SN approval. API SM/SN is for gas engines. API CK-4 or CF is for diesel engines. This is all very confusing for the average owner. Oil companies torture the English language. The very best oils don’t have to play this game.
I’ve started to change my mind about ACEA oil approvals. The ACEA is funded by the auto manufacturers. The manufacturer tells the ACEA what approval they want for their engine and the ACEA grants it. The relationship between manufacturers and the ACEA is a little too cozy. The API is much more neutral. You’ll often see the oil bottle say “Meets” the API standard. That means the oil wasn’t really tested by the API.
If the oil is a Group IV or Group V, you won’t see; distillates, petroleum, hydrotreated or heavy paraffinic or hydrogenated base oil.
If it’s a Group V oil, it plainly says “synthetic lubricant”. It may also say it has some other long chemical names. Group V ester synthetics are built from various chemicals with little to no petroleum. Since Group V oils don’t contain petroleum, they have very little Sulfated Ash. It’s Sulfated Ash that contaminates the BlueTec DPF. This is the major difference between Group V Ester synthetic diesel oil and all the others. One European Ester diesel oil is now compatible with B20 biodiesel. Group V Ester synthetic diesel oils are big in Europe, but not common in North America.
There are lots of other important qualities your oil needs. One is the HTHS (High Temperature High Shear). This is the film strength of the oil. The DPF regeneration causes lots of fuel dilution of the engine oil. The higher the HTHS, the better the engine oil resists fuel dilution. When the crankcase oil is mixed with diesel fuel the oil vaporizes even easier.
NOACK Volatility measures how well the oil withstands high temperatures. This is the blow-by that clogs the EGR and DPF. A lower NOACK rating is better.
Viscosity is one of the most misunderstood aspects. There’s a reason Mercedes dealerships in Germany use a 5W/60 diesel oil.
Fault code 170400: Check Engine Light (CEL) is on. As time goes by Mercedes publishes hundreds of Service Bulletins. If you look at each bulletin or article as a chapter in a book. First you need all the chapters, and then they need to be in the correct order. Mercedes doesn’t put the chapters in any order because they don’t want the information to be easily found. They have their reasons. Fault code 170400 is a perfect example.
Originally Mercedes said the problem was the metal exhaust pressure lines to the Differential Pressure Sensor (DPS). Then they said the EGR cooler was clogged. Mercedes didn’t say what was blocking these parts, but burnt oil was the culprit. Mercedes implies the exhaust temperature is too high, but no comment about what causes the oil to vaporize in the first place. Mechanics were told to only replace the parts. Mercedes mentions in another bulletin that NOx sensors fail for several reasons, one of which is high exhaust temperatures. Another bulletin says hot oil vapor clogs the EGR valve, EGR cooler, Intercooler, and Swirl Flaps. They said those parts also need to be replaced, with no recommendation for solving the cause of the hot oil vapor.
In 2017, enough was enough. Mercedes issued a Service Campaign using updated software to solve fault code 170400. Mercedes didn’t say what the updated software fixed, but fault code 170400 would stop making the CEL go on. You might have noticed the AEM recall stops at model year 2016. The software update is a high-tech piece of tape over the CEL. The 9/30/2021 Court case requires Mercedes to replace all the parts causing Fault Code 170400. That should tell you the fault code was very important.
Fault code 170400 is a very important fault code. It often appears in combination with other fault codes for a failed EGR valve, Swirl Flaps, Temperature sensors, DPS, DPF, or NOx sensors. Mechanics often ignore the code because it’s mixed in with what appears to be more important fault codes. Mercedes scattered the information about the code in so many different bulletins there’s no big red flag when it appears. 170400 is telling you the engine is in real trouble and you better get to the bottom of the actual problem. (Sorry, but Mercedes published a software update that removed this diagnostic fault code from the control module. The problem must have fixed itself!)
Often owners have a Check Engine Light that the dealer is too busy to diagnose. They clear the fault code and tell you to monitor the situation. When this happens, you should ask your dealer to record all the fault codes on the Repair Order. If you’re close to the end of your warranty, those intermittent fault codes may not return until you’re out of warranty. Don’t assume Mercedes will warranty the repair. Those fault codes recorded on the Repair Order are your only proof the problem existed before the end of the warranty. Clearing fault codes doesn’t fix the problem. You may not think it’s serious, but sooner or later the fault code will return with a few more fault codes to keep it company. If the dealer doesn’t mention the previous repair order, it’s often up to the owner to point it out and insist it be covered by the warranty. Repairs can be very expensive if you don’t say something.
DPF Monitor: I’ve asked hundreds of new 907 Sprinter owners if their Salesman explained anything about the DPF monitor Mercedes was forced to install in the Instrument Cluster. Dealers don’t explain the DPF monitor and neither does the Owner’s Manual. I recently spoke with the owner of a BlueTec RV about the DPF monitor and how the DPF regeneration process works. As he began to understand the complexity, he admitted his company had 4 BlueTec Sprinter Vans. It dawned on him that his Employees didn’t know anything about the most basic DPF operating procedures. They just get in and drive to their job sites. Some are short trips and others are further away. Nobody was driving the extra miles to regenerate the DPF as Mercedes recommends. He said they had a few problems but none has quit running. But as I explained how the system works, he became more worried about the potential liability. Sooner or later people will get into a situation that causes the DPF to clog. When and where that happens is a real problem. If you have Employees driving a BlueTec Sprinter, they need to understand the unusual operating procedures.
Clunking noise when going from D to R or R to D. Four-wheel drive and two-wheel drive, 906 and 907 Sprinter. The splines in the driveshaft and axle shafts need a special sealant to stop the free play.
Fault code P2459: The DPF regeneration has been interrupted 4 times. This is a very common fault code that may also have 2 additional digits. Mercedes Service Bulletin LI49.20-N-060290 covers a lot of this fault code, but not all. The basic problem is a clogged DPF or something else is causing the DPF regeneration to stop. Dealers often just replace the DPF and stop there. There’s a lot more going on, and a new DPF alone won’t solve the problem. Other parts of the system have many updates that must be repaired or you’ll keep clogging the DPF. The engine is often burning oil so that problem needs to stop. The EGR Switchover valve Y27/13 may also be clogged or defective. This is part of the EGR cooler. If it’s clogged, the Intercooler and the Swirl Flaps are also likely clogged with oil sludge.
P2459 or P2626-001 are often misdiagnosed because this is not a simple system. If you have a high mileage engine, this fault code is a bad sign. You can expect a lot more problems in different areas. People will often say they haven’t had any problems, so they will wait until they see a change. This fault code is often one of the first fault codes these owners will see. By then they’re in trouble. They can expect to see more fault codes.
Update: On 3/17/2021 Mercedes-Benz and the DOJ reached a final agreement in the second AEM diesel emissions fraud case. Mercedes will replace many more parts. If you haven’t had the AEM recall work performed on your vehicle, you must get it. Very important! Mercedes has to recall all of the original AEM-recalled vehicles and replace more parts. They say it may take 2 years before they have enough parts.
Timing Chain: Mercedes admits the Timing Chain stretches a lot faster than it should. (See Service Bulletins LI05.10-N-057796 and LI05.10-P-049909). Mercedes has redesigned the chain and sprockets for the third time. In reality, it’s the oil and excessive soot suspended in the oil that’s causing the Timing Chain and sprockets to wear so quickly. The original Timing Chain and sprockets would last indefinitely with higher quality oil, better oil filtration, and 5,000-mile oil changes.
Timing Chains can start clattering on cold starts as soon as 40,000 miles. Short trips with frequent interruptions in the DPF regeneration cause high fuel dilution. Timing Chains don’t do well with oil mixed with diesel fuel. Some Timing Chains can make it past 180,000 miles with better oil changes and less fuel dilution. Once again, this is one of the anomalies specific to each individual BlueTEC diesel and its unique operating conditions. Using the factory-recommended oil and the factory-recommended service intervals, by 80,000 miles the average BlueTEC Timing Chain is very close to its wear limit. Mercedes will pay for some timing changes as part of the AEM recall.
As the Timing Chain stretches it changes the Camshaft Timing. This causes a significant increase in NOx emissions and a noticeable drop in performance. When new, the Camshaft timing is at TDC or zero degrees at the crankshaft. As the chain stretches, the Crankshaft timing advances to its wear limit of 11 degrees. Mercedes offers an official method to measure the amount of chain stretch for both the OM642 (see AR05.10-P-7600GZB) and the OM651 (see LI05.10-N-057796). It typically cost $500 or $600 for the test. If you know where to look, it doesn’t cost anything to get a close approximation of the OM642 chain stretch. Remove the oil cap and look straight down at the piston in the Chain Tensioner. When new, the Chain Tensioner piston extends about 5mm from the body of the Chain Tensioner. When the piston extends about 13mm, the Timing Chain is at its wear limit.
B20 Biodiesel and synthetic renewable diesel fuel: Mercedes does not approve any of the B20 biodiesel fuels. Mercedes Service Bulletin LI18.00-N-054809 explains how interrupting the DPF regeneration causes fuel dilution. Your Owner’s Manual tells you fuel dilution will ruin the engine. B20 biodiesel is more common in the western USA and throughout Europe. The DPF regeneration causes unburnt diesel fuel to enter the crankcase oil. B20 fuel in the engine oil causes a chemical reaction. The oil turns into black jello and restricts the oil flow to the crankshaft and ruins the engine.
Mercedes says the 2023 BlueTec diesel engine # OM654 can use B20 with no harm. Then the 2023 OM654 warranty manual says B20 will cause engine damage and it is not covered by warranty. Mercedes doesn’t explain how this happens. It’s called “post Injection”. To increase the exhaust temperature for the DPF regeneration, Mercedes injects fuel directly into the combustion chamber. US made diesels inject the fuel into the DPF. B20 injected into the combustion chamber can wash past the piston rings and into the crankcase oil. B20 is particularly harmful if your BlueTec is not driven daily. B20 combined with the DPF regeneration process are more complicated than I can explain here. I’ve only found one European oil that’s compatible with B20 biodiesel. It’s the DPF regeneration that causes so much trouble for the BlueTec engine oil. Mercedes doesn’t fully explain the DPF operation to its dealers or owners.
BlueTEC diesels and “Direct Injection” (DI): There’s a very good YouTube video explaining DI. “Direct Injection, Problems and Solutions | The Fine Print” – https://www.youtube.com/watch?v=xrLNDgrIw3U&t=90s. This video will help you understand how the basic problems begin.
The DPS (Differential Pressure Sensor): The DPS tells the CDI computer when the DPF is full of soot and it’s time to start the automatic regeneration. Over time, the DPS gradually tells the CDI computer to regenerate the DPF more frequently than it should. This is a big part of what’s causing so much trouble.
For the DPF to regenerate:
- All the glow plugs must switch on.
- If one glow plug is out, engine starts but will not regenerate.
- The DPF finally clogs with soot and the engine stops running.
- The engine fan must come on when the DPF is regenerating. Even in cold weather.
- If the engine fan is bad, the DPF will not regenerate.
- The DPF will not regenerate when the engine is idling.
- The vehicle must be moving for the DPF to regenerate.
- If the engine temp goes over 212F, the DPF will not regenerate.
- If the “low fuel” light is on, the DPF will not regenerate.
Exhaust fumes entering the passenger cabin: People smell exhaust fumes and ask their dealer to take a look. Normally the dealer says they don’t see any exhaust leaks. This is another known problem where Mercedes has published numerous Service Bulletins about exhaust leaks. Extreme heat cracks the exhaust pipes and welds. When the flex pipe to the DPF cracks, exhaust gases are so hot the wires going to the transmission control unit melt and the engine suddenly quits. The repair costs about $3,000. If you drive a 2016 or older BlueTec Sprinter, the exhaust bracket to the DPF breaks and the exhaust falls onto the road. It normally rips a hole in the transmission Bell Housing. This is about $8,000 to repair!
Auxiliary Battery Cutoff Relay: Dealers tell owners of the 906 and 907 BlueTec Sprinters they can’t install the Mercedes auxiliary battery because the cutoff relay “E36” is missing. They just need to order the relay, p/n: 002.542.40.19 and install it. When all else fails, read the directions. Speaking of directions. The batteries in the 907 BlueTec Sprinter can be confusing. They’re not nearly as simple as you would think. Mercedes knows low voltage is at the heart of most of their problems, you can see it in hundreds of service bulletins. I know why they don’t explain it, but you would think they would be sick of it by now. Some dealers understand but they’re too busy to educate their customers. If a customer asks for it, only a few dealers will install the auxiliary battery.
The auxiliary battery is extremely important. This is also what’s causing the 907 Sprinters to pop out of PARK and roll away. Mercedes will send out the third recall for this, but it still won’t fix it. Mercedes forgot they’ve already admitted low voltage causes the problem. As of model year 2023, Mercedes has a new 280-amp alternator for Sprinters. Part number: 000.906.29.04. It can be installed on older Sprinters to recharge the batteries faster.
Ground connection: 907 Sprinter. The ground cable to the L/F motor mount can come loose or the bolt brakes. Bad ground connections can cause all types of weird electrical problems. Run a second ground cable from the engine to the frame as insurance. The ground cable for older 906 Sprinters will often corrode and the alternator not charge the battery as fast as it once did. It’s easy to see the cable. Early 906 Sprinters can have problems with the alternator not charging. Check the cable from the alternator to the starter and battery for corrosion. This is called the “Y” cable and is a common problem.
NOx system failures: Many owners with 2017 and newer BlueTec diesels are seeing NOx sensor failures. These models already have the updated NOx sensors being installed as part of the AEM recall. Why are the latest NOx sensors failing? Extreme exhaust heat is the cause. Exhaust heat comes from the DPF regeneration. Controlling the exhaust heat is critical. If you ever see fault codes P0544, P170400, or P18E100, it means the exhaust is running too hot. It will damage a long list of components, not just NOx sensors. If you have a NOx sensor failure, you should look hard at the PCV valve. A worn PCV valve lets too much oil vapor go into the DPF. That causes frequent regenerations.
NOx sensor symptoms include the No Start Countdown and the Check Engine Light. Note: You may think you have a No Start caused by the SCR countdown feature. However, the engine may not start because of blown fuses from melted wires near a DPF exhaust leak. DPF exhaust leaks also cause frequent regenerations. If your DPF regenerates every 150 miles no matter how you drive, ambient air is getting into the DPF. Check for cracks.
The fuse for the NOx AdBlue system can blow. Fault codes 155700, U029D, and U029E may be present. A complete and careful inspection of the wiring for the NOx sensors close to the exhaust system is required. Service bulletin LI49.10-N-059066 deals with this.
In other words, the engine won’t start because there’s a blown fuse in the NOx system with fault codes pointing to a NOx system failure. But what’s really happened is extremely high exhaust temperatures caused by the Intercooler and EGR cooler clogged with burnt oil vapor. Then the exhaust cracks and melts the NOx wiring and causes a short circuit to ground. It can also melt the wiring for the transmission. In that case, you’ll stop in the middle of the road. You can protect those wires with heat-reflective tape.
Note: The 907 BlueTec is having some real problems with the SCR/DEF system.
4×4 Problems 907 Sprinter: Intermittent problems when the four-wheel drive won’t engage or quits working. Some owners notice a loud grinding noise. See Service Bulletin LI28.19-N-071366 about the software update.
Oil leaks: Oil leaks are well known on the OM642 V6 BlueTEC. The oil cooler is the most famous leak. The oil cooler is no longer a problem on the newer models, but there are about a dozen other known leaks. Oil leaks are caused by excessive crankcase pressure from blow-by at the piston rings.
Fault codes / 907 Sprinter: P203B31, P203B49, P206B31 and P13DF00. All of these are software for the AdBlue tank. They’re caused by low voltage, as mentioned in multiple service bulletins.
OM651 engine failure from sudden oil loss: If you have the Eco Start-Stop feature, you better check the chain tensioner. The oil cap comes off and the engine dumps all its oil before you realize what happened. It can happen on any OM651, but it’s more common on the Eco Start-Stop.
High oil consumption: Oil consumption is caused when the piston rings become packed with burnt oil. The piston rings stick in their ring groves and can’t flex to tightly press against the cylinder walls. Compression gases blow past the piston rings and you have oil consumption. This is what also causes oil leaks. The crankcase has so much pressure it finds the weakest place and pushes oil out. Replacing a seal is only treating the symptom, not the cause. This is closely related to Bore Glazing and Bore Polishing.
High-mileage engines that burn oil normally have weak oil pumps and worn timing chains. Special care must be taken when cleaning stuck piston rings. The DPF will also be regenerating more frequently as it tries to burn off all the burnt oil. The extra heat from frequent regenerations is cycled back into the exhaust-driven Turbocharger. That additional heat increases the combustion and exhaust temperatures, making the engine burn even more oil.
Fixing this is not as simple as a different oil. You must clean up the entire system and get control of the high combustion temperatures. The Intercooler is often filled with oil sludge and can’t cool the combustion temperatures. The Intercooler must be cleaned out. A Catch Tank will stop much of the blow-by oil vapor from continually adding more oil sludge to the DPF and the air intake system. Dirty air filters and a worn-out PCV valve cause high oil consumption. Special fuel additives will help clean the varnish from the cylinder walls. You also need to make sure the oil check valves in the oil filter housing are clean and open. They can restrict the oil flow to the crankshaft. It’s not just one thing that reduces high oil consumption.
Bore Glazing: Gas engine oil, like Mercedes factory recommended oil, is loaded with friction modifiers for better fuel economy. Diesel cylinder walls run twice as hot as gas engine cylinder walls. Friction modifiers flash burn on a diesel cylinder wall. That leaves behind a varnish that fills in the machining marks on the cylinder walls. The oil doesn’t have anything to cling to, so the combustion gases from a high-compression diesel blow right past the piston rings and into the crankcase oil. That pushes crankcase oil vapor out of the PCV valve and into the EGR and air intake system..
Bore Polishing: When diesel engines idle excessively or the engine is driven frequently under a light load, the piston rings don’t press tightly against the cylinder walls. Over time that leaves a highly polished area on the cylinder walls that oil can’t cling to. Combustion gases blow past the piston rings and push the hot crankcase oil vapor out of the crankcase and into the EGR, Air Intake, and DPF. These are the reasons for using an oil with a low “NOACK Volatility”.
Gas engine oils don’t have enough “soot scatter”. Large clumps of soot in the oil are so abrasive it causes Bore Polishing. Soot also wears out the Timing Chain. These are also the reasons the Mercedes oil causes so much trouble. People on Mercedes Owners Forums claim the Mercedes MB229.52 oil is the absolute best oil for a BlueTec. They always want proof it’s not the best. That’s easy, Mercedes own data sheets verify the MB oil is nothing but conventional mineral oil. The only thing slightly special about the MB229.52 oil is its low sulfated ash rating.
The Mercedes oil doesn’t have the API or ACEA diesel approval. That means the Mercedes oil does not have enough “soot scatter” to prevent diesel soot from clumping together in the oil. Soot is what turns diesel oil black. Soot clumps together and becomes more abrasive. Actual diesel oil needs the API CK-4 or CF rating for the appropriate amount of soot scatter. API CF is an older diesel rating. It means the oil has more soot scatter than newer ratings.
Fuel system problems: The BlueTEC fuel system failure is very similar to the EGR sticking. They both feel the same. The engine can be intermittently hard to start, surge on acceleration, or intermittently die at a stop light. There’s an easy way to diagnose the problem. First, you must determine if it’s the fuel system or the EGR. Remove the fuel filter and cut it open with a special cutting tool for metal filters. Look for any metal flakes inside the fuel filter. If you see metal flakes, the High Pressure Fuel Pump has failed. The entire fuel system must be replaced. You should consider a factory-rebuilt engine. If you don’t see any metal in the filter, go to the EGR valve and remove it for cleaning. The main shaft in the EGR valve binds.
Catch Tank: The emission control laws say crankcase combustion vapor cannot vent into the atmosphere. When the engine’s running the crankcase combustion gases must be self-contained. The engine has to recycle the crankcase vapor. The BlueTEC has a PCV valve that sends the crankcase vapor into the Turbo where it continually recirculates through the EGR and the air intake system. Mercedes has updated the PCV valve 14 times. It will need to be replaced on all 2018 and older models. The PCV valve should be replaced every 50K as routine maintenance. The PCV valve slows down the hot crankcase vapor from Blow-by and Direct Injection (DI).
Direct Injection is the current fuel injection design used by most manufacturers to reduce emissions. But DI also has a downside. This design creates a lot more crud in the air intake track. Watch the YouTube video I mentioned earlier. Eventually, oil sludge coats the air intake track. The only way you can keep this crud from building up in the air intake is with high quality oil, frequent oil changes and a Catch Tank.
Catch Tanks are approved by the EPA. Mercedes cannot deny your warranty if the Catch Tank is installed properly and appropriate for the engine. The problem is, no one makes a Catch Tank specifically for a BlueTEC diesel. However, there is a billet Catch Tank that works perfectly. It removes all the dirty crankcase oil vapor that normally goes into the Turbocharger. After the dirty crankcase vapor goes through the Catch Tank only clean air is returned to the Turbocharger. The Catch Tank keeps hot oil vapor from getting into the DPF. The cleaner you can keep the DPF the fewer times it needs to regenerate. I’ll say it again, it’s the extreme heat required for burning off the soot and oil vapor in the DPF that does much of the damage to a BlueTEC.
Water Pump OM651 four-cylinder BlueTec (Service Bulletin LI07.09-N-063338): The OM651 water pump is different from any other Mercedes water pump, and not in a good way. It uses a vacuum valve inside the water pump. Sooner or later the vacuum element leaks. When it does, antifreeze is sucked into the vacuum system. You’ll typically notice the “Low Coolant” warning light comes on with no obvious leak. Do not ignore the leak and keep adding more coolant. If you ignore the leak, you’ll quickly see the CEL. Now you’re in trouble. Coolant will migrate into the Brake Booster and Vacuum Pump. From there it will move into the electrical system and contaminate the engine computer. Coolant will finally get into the engine oil and ruin the engine. It can cause thousands of dollars in damage.
There are simple ways to monitor the water pump and avoid a major repair. Mercedes has a clear filter that installs in the vacuum line from the pump. If the vacuum element leaks, you’ll see antifreeze in the filter before it does major damage. If your water pump is already leaking, the service bulletin list many of the parts you’ll need to replace. However, Mercedes Technical Service Department has special parts that aren’t in the Bulletin. The front cover of the engine will also need to be replaced. This is a 12-hour job just to fix the water pump. That doesn’t count all the damage to the electrical and vacuum systems. As I said, this is VERY EXPENSIVE.
A smart owner would replace the water pump before it leaks. Normally the OM651 water pump starts leaking between 80K and 100K. Because antifreeze can go into the electrical system, it effects the emission control system. When the CEL goes on, the DPF will not regenerate. In November 2022 Mercedes published a free Service Campaign #2022110005. This is a free software download for the water pump. The bulletin says the water pump leak “may prevent the vehicle from passing certain state inspection requirements”. I think it’s safe to say it will definitely cause the engine to fail a smog test. The software update doesn’t do anything to prevent the water pump from causing major damage. (Fault Codes: P003313, P0299FA, P0299FB, P012800, P012809 or P261F71)
Oil filtration: Diesel engines produce soot. Soot is the black nasty smoke that comes out of diesel exhaust. The soot coming from a diesel is loaded with nitrous oxides (NOx) and other cancer-causing chemicals. The days of half-hearted attempts at reducing nitrous oxides and deleting the emission system when no one is looking are over. Soot is the number one enemy of your engine and the air we all breathe.
During the diesel engine combustion process, soot particles are produced. Soot is either exhausted into the DPF or absorbed by the engine’s lubricant oil. Soot-contaminated oil has been shown to produce significant amounts of engine wear. The main mechanism of soot-related wear is through abrasion. Increased levels of soot content in the oil cause the Timing Chain to stretch. High concentrations of soot can increase the local acidic level and, around the piston where high temperatures and volatile gases coexist, corrosion will also occur.
Today’s best diesel oil will suspend soot particles within the lubricant and keep them from clumping together. Vehicle service intervals are currently dictated by the length of time that lubricants can maintain their physical properties, but also, and possibly more importantly, by the length of time they can hold soot particles in suspension. Mercedes uses a cartridge oil filter that removes soot particles down to 30 microns. There’s an aftermarket billet adapter that converts the Mercedes oil filter to a Donaldson spin-on oil filter. Donaldson filters capture soot particles down to 10 microns. Less soot in the oil means less Blow-by at the piston rings, less crud in the DPF, and longer Timing Chain life. Change the oil every 5,000 miles with a legitimate diesel oil and the Timing Chain will never fail.
Rear wheel speed sensors Recall 2021020026: Model years 2012 to 2018. This is most noticeable on RVs, but affects all Sprinters. The ABS or ESP warning lights come on.
Then there’s the dumb stuff. Broken exhaust brackets, broken bolts for the high-pressure fuel pump, High-Pressure Fuel Pump failures, OM651 water pump failures,… All of these have a repair fix.