Jan. 14, 2021 — I would like to start with saying the following comments are my own opinions.  After 50 years working with and for Mercedes-Benz as a Mechanic, Shop Foreman, Instructor, Service Manager and Shop Owner I retired in 2018.  I no longer have any affiliation with Mercedes-Benz or its authorized dealers. 

I began writing this article about 10 years ago. It started out as a way to explain the mysterious problems common to the BlueTEC diesel. Looking back, I had no idea how complicated this would become.  Dealers, Independent shops, mechanics and owners were all baffled by the endless problems. The BlueTEC diesel is unlike any gas or diesel engine ever made. Even now as Mercedes-Benz finally admits to diesel fraud in Federal Court, the problems keep coming. Let that sink in. Mercedes-Benz admits it has been lying about the problems with BlueTEC diesels not just in America, but also in Europe. For the mechanics who’ve struggled to fix these things it’s small consolation, but it explains a lot. The Press likes to say Mercedes installed a diesel defeat device. If only it were that simple. There is no such device. 

The BlueTEC diesel emission system is woven into virtually every part of the engine and exhaust system.  You may have noticed a number of websites listing the common problems with the BlueTEC diesel. They mean well, but they’re talking about the easy stuff. Unfortunately the problems have gotten much more complicated. This is no exaggeration. Mercedes-Benz and other manufactures didn’t trash their reputations simply because diesel emission technology is difficult. It’s beyond difficult. on one hand I can really appreciate the difficulty. But on the other hand they’ve brought this upon themselves. Every year I find it’s more difficult to succinctly explain what actually causes the wide variety of problems most owners will eventually experience. While the diesel fraud settlement clarified the most difficult aspects, it’s made it more difficult to explain.

BlueTECs are sold to a public expecting something far different than what they’ve bought. I realize most owners don’t read the Owner’s Manual. But for the owners who will read the Owner’s Manual, they should be able to find all of the important operating requirements. In my opinion Mercedes omits important technical information. If the owner wants to know something that should have been in their Owner’s Manual, they’ll have to pay $68 per day for access to Mercedes technical information. The problem is, owners don’t know what’s missing? The Sales Brochure says the oil is changed every 20,000 miles. But if the owner pays $68 and searches Mercedes technical website they’ll find a completely different service schedule that advocates much more frequent oil changes. The Owner’s Manual warns of engine failures related to the DPF regeneration. But Mercedes omitted 99% of the information about the DPF regeneration. They put it on their $68 website. Once again, how can the owner possibly know there’s more to the story and where they should go to find it? I forgot, ask your dealer. Or you can go to: https://www.startekinfo.com/service/download-document/outside/224766/ and you’ll find the instruction manual for using the Mercedes-Benz technical website.

I recently spoke with someone who just paid $250,000 for a spectacular BlueTEC Sprinter RV. The RV Salesman spent hours explaining the coach and how it works. When it came to the engine and maintenance, see your Mercedes-Benz dealer. When the owner went to the Mercedes dealership, they got ten minutes with whoever wasn’t busy. There’s no one to explain all the unique preventive maintenance that never made it into the Owner’s Manual. This machine operates on public highways. Owners have a right to easy access to technical information. Simply put, owners have no idea what they’ve really bought. Since the BlueTEC was introduced in 2007, I’ve spent every day working on this system and I still find it difficult. It’s like trying to explain a bowl of spaghetti. I think most people willing to spend over $100,000 for a Sprinter RV would actually pay attention to the preventive maintenance if someone actually explained how their new BlueTEC operates. Driving a BlueTEC requires owner participation. BlueTEC’s have too many complicated systems for owners not to understand their operation. Instead owners are told to keep the AdBlue topped off and take it in for service every 20,000 miles. Mercedes thinks they’ll lose sales if they really explain the BlueTEC diesel. They might lose some, but I talk to a lot of people will do the preventive maintenance if someone explains what and why things are done. Engineers and mechanically inclined enthusiast actually love the challenge of a BlueTEC. It’s more of a hobby or lifestyle than basic transportation. Sprinters are a blast to take on and off road. I get it. But for owners who don’t understand the BlueTEC, it can stop being fun in a hurry.

I ask new owners if their Salesman explained the DPF monitor? No one has ever told me their Salesman or a Service Advisor ever explained the DPF monitor. Starting in model year 2019, Mercedes includes the DPF Monitor. The DPF is the “Diesel Particulate Filter”. The DPF is located in the exhaust system. It filters the black soot and burnt oil going through the exhaust. Once the DPF is full of soot the emission system automatically burns off the soot much like a self cleaning oven. This is known as the DPF regeneration. The DPF typically regenerates every 300 or 400 miles. The heat cycle normally takes 15 to 25 minutes. And as they say, this is where the trouble starts. Over time, it’s the extreme heat cycles that does all the damage. If you reduce the heat cycles, you’ll reduce the mechanical failures and the repair cost. When you read about the common problems most owners complain about, they can all be traced back to the DPF’s extreme heat cycles. The extreme heat also puts a heavy thermal load on the engine oil. Normal synthetic oil can’t handle the extreme combustion temperatures for the DPF regeneration. The oil gets so hot it vaporizes and finally ends up in the DPF along with the soot. If you can keep the oil out of the DPF you’ll save yourself a lot of maintenance cost. Depending on your situation, there are lots of things you can do that will prevent the oil from getting into the DPF.

Mercedes knows sooner or later every owner will have problems with the DPF.  Yet the 2020 Owner’s Manual barely mentions the DPF Monitor.  The 2019 Owner’s Manual doesn’t say anything. If you go to my separate Blog Post about the DPF monitor, I explain what it does and why it’s so important. I don’t know how anyone can drive a BlueTEC diesel without knowing what’s happening in their DPF. It’s like driving without knowing how much oil is in the engine or how much air is in the tires. Mercedes now sells a DPF Monitor (p/n: 906.900.34.04) for the 2018 and older models.  But like the new models, the operating instructions are totally inadequate.  Most dealers don’t even know Mercedes makes a DPF Monitor.  I’ve written the complete instructions for both versions. Contact me and I’ll send you a pdf file.

As I said earlier, people who drive a BlueTEC diesel must be active participants.  You can’t wait until warning lights come on.  The further you can go between automatic regenerations the easier life is for your engine and emission system. Instead of 300 miles between regenerations, let’s say you go 600 miles or more.  That makes a big difference in the wear and tear in the engine. But you have to pay attention to what’s going on with the DPF.  You can take a picture of your odometer each time the DPF regenerates.  If you switch to a different oil or fuel additive, you’ll know for certain if you made an improvement.  Better oil doesn’t evaporate as easily with the extreme heat. Oil vapor mixes with the exhaust soot in the EGR and ultimately ends up in the DPF.  Better oil means the DPF doesn’t need to regenerate as often.  As the oil wears out more of it goes into the DPF.  The DPF has to regenerate more often. If you’re watching the DPF Monitor you’ll see that.  There are a number of common things that will interrupt the regeneration. The DPF can clog and the engine can stop running.  You’ll see that if you’re watching the DPF Monitor. 

For a real eye opener, go to the DOJ website and read the fraud agreement Mercedes reached with the EPA, CARB and the DOJ.  The agreement includes a recall on all 2009 through 2016 OM642 and OM651 BlueTEC diesels. The agreement also extends the warranty on quite a few expensive parts. The recall should have started last October, 2020.  I’m sure the recall will happen. The rumor is the Court is not satisfied with the agreement. Like everything else with a BlueTEC the recall is also complicated.  In order to reduce NOx emissions, Mercedes agreed to replace a number of expensive parts. This is a big help, but don’t expect Mercedes to pay for anything that might be wrong with your BlueTEC. The guidelines are strict. If you’ve deleted your emission system, don’t expect any help.

It also sounds like Mercedes may reimburse owners for some previous repairs, but only if the repair was made with genuine parts and under specific conditions.  This is where things get murky.  Were the previous repairs done properly?  A few days ago the owner of a 2012 OM642 Sprinter contacted me about a problem he was having with his Turbocharger.  His dealer replaced the Turbo a couple of years ago.  A few months later the new Turbo failed.  The dealer replaced it under warranty.  Now the Turbo has failed again.  The dealer wants him to pay dealer cost for a new Turbo and the dealer will pay the labor.  On the surface that sounds fair.  But the owner wants to know why the Turbo keeps failing?  The owner didn’t know much about the fraud case with Mercedes.  I explained the Turbo is one of the things Mercedes will extend the warranty to 11 years or 120,000 miles.  The owner has 123,000 miles on his Sprinter.  The dealer didn’t mention the recall and that’s understandable. Mercedes hasn’t finalized everything and dealers also don’t know what’s happening.  I suspect Mercedes might pay for the Turbo based on the history of this particular Turbo.  But why three Turbos?  I looked at his Repair Orders and the dealer replaced the Turbo, changed the oil each time and cleaned the Intercooler.  But Service Bulletins LI14.10-N-049797 and LI09.40-N-063089 both tell the dealer to check for metal in the EGR and Intercooler.  If they find metal they should clean and replace the EGR and Intercooler.  The Bulletins also say they should replace the exhaust manifolds with updated parts.  Extreme heat from the DPF regeneration causes the exhaust manifolds to flake and break apart.  The Turbo sucks in the metal flakes and damages the impeller.  But there’s more.  Service Bulletin LI09.40-P-063552 says sludge can block the oil passages. The oil pump and check valves become clogged with burnt oil. The Turbo starves for oil.  Bulletin LI09.40-P-054328 says the oil passages in the Turbo’s pedestal are also restricted with burnt oil.  The pedestal has been updated twice and should have been replaced with a new Turbo.  None of these were listed on the owner’s Repair Orders.  The exhaust manifolds should also have been replaced.  The oil pan should have also been checked for sludge.

Because of his mileage I asked the owner if he heard a metallic rattle from the engine after a cold start?  He said he had been hearing that for a while.  He thought it was something with the Turbo.  The metallic noise on cold starts is the Timing Chain.  The chain has stretched beyond its wear limit.  The Timing Chain is also on the list for the extended warranty of 11 years or 120,000 miles.  When the Camshaft timing is thrown off by a stretched timing chain the NOx emissions increase. Lovely, with 123,000 miles, it’s not likely Mercedes will pay for these things. 

So how should the owner handle these problems? I get these calls all the time. The best way is to step back and see complete picture. What are all the possible problems and how do you get to a baseline? Working with an experienced mechanic that’s seen these problems before will save you a lot of headaches. So many times owners jump in and fix the current problem. Depending on the model and milage BlueTECs all tend to have the same problems. Even if this owner fixes the Turbo and all the other things mentioned in the Bulletins he will still have a bad timing chain. Throw in all the other known problems and you’re at the cost of a factory rebuilt engine. But is that even the end of the repairs? People think they get a new engine and that’s everything they could possibly need. Wrong! The engine doesn’t include all the exhaust and DEF system parts. Some of those Mercedes may pay for with the recall. When you add all of this up, it’s easy to exceed the value of the Van. Nobody ever told this owner about better oil or the proactive repairs Mercedes has published bulletins about. It’s a hard lesson. If someone had explained the proper maintenance for his driving conditions he would have never had these problems. Even the parts in Mercedes service bulletins will normally be fine if you’re proactive with maintenance.

Mercedes is good about publishing preemptive repairs in their Service Bulletins. The problem is nobody tells the owners. There were lots of chances to avoid his current situation.  But how does an owner know there are Service Bulletins with additional repair information?  Shouldn’t the dealer be responsible for the proper repair?  What if the engine had 119,000 miles?  Who tells the owner about all the other repair possibilities and the correct way to make the repair?  I’ve talked to hundreds of owners who paid for lots of the parts on the extended warranty list.  Unfortunately, his engine finally locked up because the oil pan was full of sludge just as Mercedes describes in Service Bulletin GI01.10-P-056315.  The engine is ruined and the cost of repair exceeds the value of the car.  Most of the parts on the extended warranty list already have Service Bulletins about the part. Now more than ever you need to work with a Mechanic who understands the parts on the list and how you can make the most of this opportunity. There’s a lot of money at stake.

Most of these problems have a common cause – the engine oil breaks down and accelerates the failures.  The 2017 and newer Sprinters are not in the recall. If you don’t make the preventive repairs now, you’ll have the same problems.  Proactive maintenance is the only way to avoid the extreme heat caused by frequent regenerations of the DPF.  Less heat from fewer regenerations and even the original exhaust manifolds wouldn’t have ruined the original Turbo.  The original Turbo would still be going strong, because the oil passages wouldn’t be clogged with sludge.  The Timing Chain wouldn’t be stretched past the wear limit.  I explain this in a separate Blog article about the oil.

–  Timing Chain: Mercedes admits the Timing Chain stretches faster than it should.  (See Service Bulletin LI05.10-N-057796).  Mercedes redesigned the chain and sprockets for the third time.  In reality, the oil caused the Timing Chain and sprockets to wear out so fast.  Quality oil with 5,000 mile changes and the original timing chain will last the life of the vehicle.  Some chains will start rattling on cold starts as early as 40,000 miles while other chains will last over 100,000 miles.  The average BlueTEC Timing Chain is near its wear limit at roughly 80,000 miles. 

As the Timing Chain stretches it changes the Camshaft Timing.  The engine doesn’t run as well and the NOx emissions increase.  The Camshaft timing on a new engine starts out at zero degrees on the crankshaft.  Over time the chain stretches and the Camshaft timing advances.  At 11 degrees advance on the Crankshaft the chain is at the wear limit and chain needs to be replaced. 

Chain stretch can also be measured.  Let’s say you measure your Chain and it has advanced 9 degrees at 80,000 miles.  You’re getting very close to the wear limit.  A Timing Chain and sprockets is a $5,000 repair.  You can continue driving until the Chain is shot; or you can switch to a different type of oil.  A few years ago, I suggested certain motorcycle oils could prevent the Chain from reaching its wear limit.  The Owner’s Forums had a cow.  Some people on the forum were mortified that I would suggest motorcycle oil in a BlueTEC diesel.  Go ahead, replace the Timing Chain.  It’s fine with me.  Or, you can use an Ester synthetic motorcycle oil with the API “CF” diesel approval. 

Yes, most motorcycle oils with the API “CF” diesel approval has more Ash.  But Ester synthetic is naturally cleaner with less Ash. Installing a Catch Tank prevents most of the harmful chemicals from even low Ash oils designed for protecting the DPF. Ash poisons the DPF because Ash can’t be burned off by the regeneration. The purpose of a Catch Tank is to prevent crankcase Blow-by oil vapor from mixing with exhaust soot as the oil vapor passes through the EGR valve. It’s this toxic mess that builds up in the air intake system before it finally enters the DPF. You can compromise or buy a new engine.  Or better yet… use Break-in oil in your next new engine. Use the appropriate oil for your climate and driving style. Change the oil every 5,000 miles and you’ll never hear a peep about the Timing Chain.

Engines with worn Timing Chains are often burning oil.  BlueTECs burn oil because the piston rings are packed with burnt oil and the Cylinder Walls are Glazed.  The piston rings are stuck in their ring grooves. The piston rings can’t press tightly enough against the polished cylinder walls.  High detergent flushing oils can free-up the piston rings. Special fuel additives can slowly remove the burnt varnish on the cylinder walls.  I’ve cleaned up engines this way that were burning a quart of oil every 200 miles. Persistence and proven methods will bring a BlueTEC back from the brink, but only if the Timing Chain hasn’t stretched past its wear limit. If the engine has high oil consumption and the chain is slapping on cold starts — there will be to many ancelerry problems. The party is over.

–  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 really help you understand how the basic problems begin.

–  AdBlue, DEF, SCR (Selective Catalytic Reduction) and NOx sensors:  This is the area covered by the fraud recall.  SCR and DEF are used to reduce NOx.  The SCR has several sub-categories which need their own detailed explanations.  Owners have problems with one part of the system and they hope they can limit the repairs to that one area.  The most common problems are with the AdBlue tank and the NOx sensors.  This is the system that causes the “No Start” countdown.  It’s also the most common cause of the “Limp Home” loss of power mode.  Once again, it’s simpler to prevent the problem then it is to dig out of the hole.  Even though Mercedes has admitted that all the early AdBlue tanks will fail, I’ve shown lots of owners how to prevent the failure.  #1- Keep the tank full.  #2- Use genuine Mercedes AdBlue.  #3- Flush the tank every 2 years.  #4- Clean the Dosing valve every 40,000 miles.  #5- Reduce the exhaust temperatures.  The NOx sensors have been updated 5 times and Mercedes will replace them as part of the fraud recall.  But extreme heat is the main cause of NOx sensor failures.  If owners had done these 5 simple things when their vehicle was new, they wouldn’t have problems now. 

Mercedes will eventually fix some of these things as part of the recall. But you may have to wait up to 3 years before it’s your turn.  If you have problems now, there’s no time to wait.  Mercedes has updated and modified virtually every part in this system.  Delaying the inevitable only means the repair cost will increase.  No shortcuts. The frustration for most owners is no one at Mercedes will explain the entire system and what actually needs to be done. It’s definitely doable. Instead, dealers fix things one by one as they break. They fix the symptom but not the cause. Mercedes hasn’t made it easy, but if you diligently follow all their technical bulletins there’s actually a roadmap to reliability. It’s slightly different from one year to the next. The higher the mileage the more work needs to be done. And there is a tipping point where the repair cost will outweigh the benefits. Once the Court gets this sorted out, Mercedes should reimburse you the covered repairs. At this moment it’s better to proactively perform the preventive repairs and wait for your recall notice. If you’re having problems that must be repaired now, you should ask for two repair orders. One for repairs you know won’t be covered. The second repair order is for repairs listed in the Court Settlement. Once Mercedes notifies you of the recall, you can ask Mercedes-Benz for reimbursement. You don’t want routine repairs mixed up with recall repairs.  

–  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 causing so much of the extreme heat.  Over the years this has been one of the hardest problems to thoroughly understand. Mercedes published many service bulletins about the DPS. But no single bulletin explained the complete problem. The DPS affects other parts of the system that aren’t so obvious. For years no one had any idea this is where the problem originated.  Even now, it’s not as simple as just replacing the DPS. Most experienced Mercedes mechanics think this matter is solved as of 2016. But it appears model years 2017 and 2018 may also experience problems with the DPS.  From the many owners I’ve talked to, there’re plenty of dealers who still don’t understand this part of the system.  This happens so slowly people think they’ll wait until they see a problem.  If you wait until you notice the problem, you’ll have missed your opportunity.

–  Exhaust fumes entering the 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 many Service Bulletins about exhaust leaks.  The extreme heat caused by the DPF regeneration will crack the welds in the exhaust.  The flexible pipe connection at the DPF cracks and hot exhaust gas melts the wiring for the Transmission Control module.  The wiring shorts out and you come to a sudden stop.  If the Transmission Control module shorts out it will cost you $2,000 to $3,000…. if you’re still alive.  There’s an easy way to prevent this.  

The extreme heat causes the bracket holding the DPF to eventually break.  The DPF falls onto the road and give the people following you a gift they will never forget.  The Bracket is attached to the Bell Housing of the transmission.  When the bracket breaks it rips a hole in the Bell housing.  The $40 Bracket has been updated twice.  Did your dealer did tell you about the bracket or are they waiting for this $6,000 repair to make their month?  See Service Bulletin LI49.10-N-067486.

–  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 the blow-by at the piston rings.  Some leaks are cheap to fix and others are very expensive.  I’ve put together a pdf file with all the oil leaks and the cheapest way to stop them.    

–  Fuel system problems:  The BlueTEC fuel system has two delivery pumps in the fuel tank.  Fuel is pumped through the fuel filter and into the High Pressure Fuel pump (HPFP).  The HPFP increases the fuel pressure to 23,000 psi.  From there it does into the fuel rails and injectors.  The fuel system typically fails because the diesel fuel had gas or water mixed in the fuel.  Gas or water damages the HPFP.  Tiny flakes of metal from the HPFP goes into the fuel rails and injectors. That’s all it takes and you’re looking at $17,000 to replace the fuel system.  Mercedes will not warrantee the fuel system.  There are ways to protect the HPFP.  B20 biodiesel is another problem.  More stations are selling B20 and not marking it on the pump.  B20 biodiesel will clog your fuel filter and turn the engine oil into jello.  There are special oil and fuel additives for B20.  But it’s better to avoid B20 at all cost.

–  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 60K 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 into 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.

–  Oil filtration:  Diesel engines produce soot.  Soot is the black nasty smoke that comes out of a diesel exhaust.  The soot coming from a diesel is loaded with nitros oxides (NOx) and other cancer causing chemicals.  The days of half hearted attempts at reducing nitros 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 breath.  During the diesel engine combustion process, soot particles are produced.  Soot is either exhausted into the DPF or absorbed by the engine’s lubricant.  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 causes 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 adapter to convert the Mercedes oil filter to a Donaldson spin-on oil filter.  It filters 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 and replace the Mercedes oil filter every 2,500 miles and the Timing Chain will never fail.

–  And then we have the dumb stuff:  Things that should never happen.  Starting in 2019 the OM642 diesel doesn’t come with an engine oil dipstick.  Mercedes puts a cheap oil plug in the dipstick tube that often blows out and sprays oil all over the engine.  

New Sprinters also have a problem with one of the Power Steering hoses popping off a fitting at the radiator.  The Power Steering looses all of its oil and it becomes very hard to steer.  Mercedes has been screwing around with this problem for 20 years.  Mercedes says you should install a different hose clamp.  The problem is not the clamp.  The problem is the hose is about 13mm too short.  Over time the movement of the engine pulls the hose off.  There’s an easy way to lengthen the hose with a magnetic Power Steering filter and a better clamp.  See Service Bulletin LI46.00-N-068838.

If you own a OM651 4 cylinder BlueTEC, you’ve got some all time stupid problems.  The OM651 has the goofiest water pump in the world.  Its design allows coolant to enter the engine’s vacuum system and eventually enter the electrical, brake booster and vacuum pump.  If you ignore the “low coolant” light it can ultimately ruin the engine.  This repair is outrageously expensive.  There’s a simple way to monitor the problem and catch it before it causes so much damage.  See Service Bulletin LI07.09-N-063338.

The OM651 also uses a single roller timing chain that’s at the rear of the engine.  The engine and transmission must be removed to replace the timing chain.  Once again, the repair cost is outrageous.  Protect the Timing Chain with frequent oil changes.  See Service Bulletin LI05.10-N-057796.

The OM651 is a good engine but it has some peculiar problems that are unique to the OM651.  I’ve put together 3 manuals that cover all the problems and how to prevent them.

For years, Sprinter owners have complained about howling noises from the front or rear differentials.  Year after year Mercedes publishes Service Bulletins that say they are investigating the problem.  (See Service Bulletin LI33.30-N-071003.) The noise is actually caused by “fuel efficient” differential oil that damages the bearings in the differential.  Change the differential oil to Castrol ‘SAF XJ’ 75W/140  MB p/n: 001.989.52.03.10, ASAP.  You’ll also need a magnetic drain plug, p/n: 000.990.58.17.  See Service Bulletin S-B-00.20/102a.

Sprinter owners have complained about intermittent clunking noises from the driveline on load changes.  The noise is caused by excessive free play in the splined connections of the drive shaft and axle shafts.  They need to be removed and coated with a thick glue called OmniFIT 100H.  Mercedes published Service Bulletins about this same complaint 40 years ago.  They used the same OmniFIT to stop the noise.  See Service Bulletin LI35.30-N-049982.

Some late model 907 and 906 Sprinter’s with the OM642 report an intermittent problem of no power when the engine is near freezing. Often at high altitude.  After the engine warms up for a minute it runs normal.  It may do this very intermittently when driving in cold weather at high altitudes.  Most of these are still within warranty. I won’t say nobody knows what’s causing this, but it’s rumored Mercedes has bought back a couple of Sprinters because of this. See Service Bulletin LI14.20-N-071638: The EGR cooling solenoid valve (Y27/13) intermittently sticks causing a lack of power. You may or may not find Fault Code P2459. I think condensation is getting in the valve and it freezes. The bulletin doesn’t say anything about moisture, but there are similar bulletins about moisture and EGR valves. When the engine warms up the moisture thaws and the solenoid starts working again. A shop test always shows the solenoid is normal because it’s not cold enough. Plus there needs to be enough moisture in the air to make it freeze.
Another possibility is the EBP (Exhaust Back Pressure Sensor / in the EGR cooler), the DPS (Differential Pressure Sensor) and the IPS (Intake Pressure Sensor p/n: – green label) may need to be replaced or have a “Teach-in” performed.
Don’t forget, the wrong oil viscosity in cold weather can also cause the engine to feel sluggish after a cold start. Use the appropriate 0W/40 oil viscosity in extreme cold. If you drive in constant subzero temperatures, there are other oils for that. An Ester based synthetic 0W/30 would be the best choice. Ester synthetic flows better in extreme cold. There are Block heaters, fuel, battery, oil and AdBlue tank heaters for subzero weather. You should also give the engine a couple of minutes to warm-up in subzero weather. Start the engine and raise the idle to about 1,000 RPM’s. Then start driving.

Service Bulletin LI03.10-N-071148 – dated 6/4/2020 (OM642 and OM651): Rough idle caused by bent connecting rod on one cylinder. Condensation has entered the Intercooler (Charge air system) causing one cylinder to hydro lock. Compression is slightly lower on cylinder #6 in the OM642 and cylinder #2 in the OM651. The engine is ruined. This applies to all Sprinter chassis 907 and 906 with the OM642 and 906 with the OM651 up to production date 2/2019. After that date the Intercooler and hose were updated at the factory. This is not common, but it has happened. Here’s the tough part of this problem. What if the connecting rod is slightly bent? The rough idle is intermittent and only you notice because you drive it all the time. Maybe the idle is slightly rough when the engine is cold. It is not a Recall, but it sounds like Mercedes might preemptively replace the Intercooler and hose as Goodwill. It wouldn’t hurt to ask. Mercedes doesn’t say what causes the condensation. They only say it happens “under certain conditions”. I suspect it happens in areas with colder weather and high humidity. The updated part numbers are in the bulletin. This also applies to custom RV’s. Upfitters are not allowed to alter things like the Intercooler. It’s not that expensive so if you drive in a humid climate and don’t need the aggravation, you might pay for the repair yourself. Engines are often on backorder for several months.

Service Bulletin LI20.30-P-069996 – dated 7/2/2019 (OM642 and OM651): Oil in the cooling system. The Heat Exchanger is warped and oil is leaking into the cooling system. Oil is in the coolant recovery tank. The Heat Exchanger is attached to the Oil Filter housing. Replace the complete Heat Exchanger and not just the gasket. Replace the Coolant Recovery tank. Follow work instructions in the service bulletin. Don’t forget, Mercedes changed the type of antifreeze in April 2014. Prior to that date the antifreeze is Blue, p/n: Q103.00.04. After that date the antifreeze is Pink, p/n: Q103.00.05. Flush oil from the cooling system with Cooling System Cleaner, p/n: 002.986.42.71. You may need to flush the oil several times. Oil in the cooling system will attack any rubber hose or seal. If oil has been in the system very long, over 3 months, you’ll have problems with leaks. Don’t forget, the radiator has rubber seal between the plastic tanks and the metal cooling fins. If this happens on the OM651 four cylinder diesel, you’ll have a much bigger problem than can be explained here.

The High Pressure Fuel Pump can work loose and cause a knocking noise at idle.  Mercedes says mechanics should ignore the noise.  (See Service Bulletin LI07.16-N-070308)  But Mercedes training documents tell a different story.  The Training Center says the High Pressure Fuel Pump can work loose and break one of the three bolts holding the pump to the engine block.  The High Pressure Fuel Pump works loose and jams the Timing Chain.  (OM642 and OM651)  That breaks the Camshaft Gears.  This is an easy $8,000 repair that’s easy to prevent.  The mounting bolts have been hardened and are made with thread locker; p/n: 001.990.93.03.  The 3 bolts cost less than $5 and take less than 5 minutes to replace.  It’s your call.  See Service Bulletin LI07.16-N-070308 dated 9/2019.  (If the bolts are tight, and you still have the knocking noise, the fuel does not have enough lubricity.  You should not ignore a knocking noise from the High Pressure Fuel Pump.

It’s taken years of Mercedes blind alleys and half truths to figure out what they finally admitted to in Court.  Each bit of information helps sharpen the focus.  In this fraud settlement Mercedes-Benz has paid the EPA, CARB and Lawyers billions of dollars.  I don’t see them helping BlueTEC owners with anything.  When Mercedes finally notifies you about the recall it will be better, but still won’t be the end to the problems.  There are loads of other problems like the ones I’ve listed here.  I’ve had to edit and expand much of the information I had previously sent to owners who had asked for help.  I was charging $200 which went to my Grandson’s 529 College savings account.  I’ve learned a lot from talking to BlueTEC owners around the World.  I’ve never met a single person that didn’t appreciated the help.  Unfortunately the BlueTEC technology has gotten even more complicated.  The learning curve for a BlueTEC diesel is so steep.  This stuff is hard.  It’s not something the average owner will enjoy.  And they shouldn’t have to jump through hoops to own a BlueTEC.  But the cost of updating so many parts has put the BlueTEC out of reach for most owners.  They’ll fix what breaks and hope it doesn’t get worse.  Most owners aren’t interested in making a hobby out of their BlueTEC diesel.  However, a small percentage of owners do enjoy the challenge of understanding their BlueTEC.  They like to go way off the grid.  It’s a good feeling when you know you’ve taken every percussion.  You know something stupid is not going to happen when you take off down a rough dirt road.  I’ve rewritten the article with these self reliant enthusiast in mind.  I also hear from business owners who rely on their Sprinter every day.  Putting their Van in the shop every few months is not good for business.  They bought a Sprinter to be an asset for their business, not a liability.  If you have employees driving a BlueTEC they have to understand how the DPF Monitor works.  I’ve spoken with many Shuttle Van owners who’s employees and passengers have been stranded when the DPF clogged up.  Giving your driver a DPF Monitor with instructions they can understand should give you some peace of mind.

The cheap and easy fix was when it was new.  Some people think they have a new Van and it’s covered by the warranty.  I’ll worry about it when the warranty is over. Believe me, it’s way cheaper to prevent a problem then wait until it happens. Who cares if Mercedes will tow you 400 miles from Zion National Park.  This is for owners who never want to call a Tow truck. These owners want an advocate on their side.  I’m sorry, but I had to raise the price to $500.  It still goes to the same 529 College Savings account. I don’t expect people to spend $500 without knowing what to expect. If you think you may want more help, call or email me and explain you situation.

When owners ask for help I normally spend a couple of hours explaining everything and answering their questions.  Depending on their situation I go over all the things they need to do in order to avoid problems. For example, let’s say there are 20 things on your Van that have the potential to fail. Each one by itself has a 5% chance of failing. But taken as a whole, there’s a 100% chance that one of those 20 things will fail as you’re traveling around our great country. I’ll go over all the stuff on your list of potential problems and you can decide what you want to remove from the list and what you want to take a chance with. The list is different for everyone. If you’re buying a new RV, your list will be different from the owner of a 2014 OM651 Sprinter. After I’m sure we’re on the same page with technical comfort level I send emails explaining everything we talked about.  I attach pdf files with all the documents related to their vehicle.

Most of what I send is stuff Mercedes has published or admitted to. Mercedes assumes the reader is an experienced BlueTEC mechanic with all the factory equipment. I assume I’m explaining it to someone who’s not a factory trained mechanic. The odds are you’ll still need to rely on the trained mechanic. But now you’ll be able to communicate with each other. Mechanics actually prefer dealing with customers who understand just how complicated their vehicle actually is. I don’t sell any products. But I do explain what to get, part numbers and where to order things. I prefer to use genuine Mercedes-Benz parts and procedures as possible. Like the DPF monitor. Other companies make DPF monitors. But if you have a problem while traveling I don’t want you going to a Mercedes dealer and trying to explain some hair brained part or procedure you found on the internet. It’s a genuine Mercedes DPF monitor and it’s indicating a problem with the DPF, the dealer should know how the genuine Mercedes-Benz DPF monitor operates. When I explain various procedures, the odds are they came from Mercedes. This is not about bashing Mercedes-Benz. There’ll be some exceptions but not very many. If you have questions, you can call as many times as it takes.  If you want more information you can email me at: tom54stephens@gmail.com. (Tom Stephens 916.715.0665)