Originally Posted by Diabolis

No, not viscosity - I do mean lubricity. It's a property of how slippery the fuel is and how much of it gets past the piston rings (it has nothing to do with the injectors). Biodiesel has higher lubricity than dinosaur juice diesel so more of it ends up in the crankcase.

The biggest killer of timing chains (both the earlier double row and the later single row ones) is carbon - soot - suspended in the oil. So, timing chain failures again boil down to long oil change intervals. If you were only changing the oil only as often as the recommended OCI, you have your culprit. The fact that the prescribed OCI by Mercedes was far too long for some states where the government changed the game and decided to subsidize corn and soybean farmers and the diesel pumps started spewing out B20 instead of the maximum B5 that the engines were designed and built for is technically not Mercedes' fault. We do UOAs every 8K kms and usually go 16K kms (10K miles) or 24K kms (15K miles) on the Sprinters, but we only have a maximum B5 content. None of the five Sprinters we have or my ML have had timing chain issues - and the Sprinters have *way* over 120K miles.

As for the rest of the MLs and GLs, all of the ones sold in NA were built in the Tuscaloosa, Alabama plant after Daimler's divorce from Chrysler - so yes, they are indeed crap compared to luxury vehicles that were built in Germany or Japan and imported here. That's unfortunately par for the course and not in any way unexpected. While Mercedes managed to eventually improve quality control at that specific plant over the next few years after they completely revamped literally every single process on every production line, the stuff they were making back then - and to a somewhat lesser extent, the stuff they are still making now - was/is indeed garbage by German or Japanese standards.

Originally Posted by John CC

That's funny, because when we went to ultra low sulfur fuel the process to remove the sulfur was said to reduce the lubricity of the fuel and the result was problems with some of the injection pumps, particularly the Stanadyne and Roosa Master rotary style. Just goes to show one man's not enough lubricity is another's too much...

Also, how much can get past the rings? Isn't it supposed to burn?

Originally Posted by John CC

Also, how much can get past the rings? Isn't it supposed to burn?

Originally Posted by SeanyF

thanks for another follow up. I’m enjoying this back and forth and appreciate you taking the time.

ok, so we’re more or less on the same page then regarding the lubricity.

in my first post I asked if it was caused by it sticking to the liner walls, which from the sounds of it it is. It gets scraped down by the scraper rings in larger amounts.

I guess the only other part then is why is there enough of it in the cylinder to start with that it’s sticking to the liner instead of getting burnt? That’s not normal at all.

I would wager that the lubricity also means that more of it slips past in the injector meaning a slight excess of fuel in the chamber. I would assume that the metering of fuel in the injector is done within a certain range of properties, e.g. viscosity and lubricity etc. that would have been programmed when B20 wasn’t around yet.

I wonder if a software update to tell the car that to meter less fuel per stroke and retard the injection quantities accordingly could solve that problem.

you’d imagine that excess fuel in the chamber would result in a lot of other problems too, like after burning etc.

interesting one for sure. I’ll read up on it. It’s new to me because we don’t have the same level of biodiesel as you guys do.

regarding the timing chain stretching, when your doing the oil analysis are you seeing high levels of carbon build up in the oil in general? Is that what you’re using as a marker for when to change the oil?

we run caterpillar 3516’s at work and those have a centrifugal filter to take the carbon out. In theory you don’t have to change the oil till a sample comes back bad, but we do it at 1000hr intervals.

Originally Posted by kajtek1

I guarantee you MB did not design it this way.
After AEM I recheck my vehicles and mechanic doing the modifications did run the wires against sharp edges of heat shield. That was just 1 of whole list of issues I had to fix after doing AEM on 4 vehicles.
Meaning job ethics with US mechanics don't really exist and once you start taking car to mechanics, that opens a chain reaction.
My OM642 in Sprinter is about 210k miles and purrs like a kitten. Only thing I had to do on it in 3 years, was oil change and once I had to add refrigerant to rear AC. Driving MB exclusively for last 25 years, rough estimate says that I spend average $30 a year on parts replacement (plus regular maintenance)
Sorry to hear about your bad luck.

Originally Posted by Diabolis

Ugh... looks like we've hit a nerve here, and based on your last post it is apparent that you really are clueless. The fact that you are erroneously grouping together a "5 starts remaining" message and the OM642 engine itself says plenty about your level of knowledge. You wouldn't happen to be Tom Stephens of Stephens Service Center by any chance, would you?

I am sorry to hear your experience has been that negative - mine thankfully hasn't, and moreover I know of a VERY few instances in Canada that have resulted in catastrophic engine failures (this is based on statistical information directly from MB Canada, not a second hand account or a handful of cars that people have brought in). Unlike in the USA, 86% of all W166 and X166 MLs and GLs sold here were the 350 Bluetecs, or roughly some 32,000 vehicles. In comparison, the total number of W166 and X166 diesels sold in the US was less than half of that. Yet, the only people *****ing and moaning about the OM642 are owners from the USA that have admittedly been dealt a bad hand with their biofuel subsidies and resulting biodiesel content - for which you need to blame your government, not Mercedes - and are either too stupid or too cheap to change the oil any more often than they have to in order not to void their warranty. They also don't seem to understand that a DEF heater that dies after 5 or 6 years of freezing and thawing cycles does not make the engine crap and is technically considered a wear and tear item. The OM642 has been around since 2005, and is still being made and used today as a diesel workhorse, not just by Mercedes but also by Chrysler. Name one other modern engine that has been in production for 18 years please. And, if you think the OM642 is problematic, you really ought to have a good look at the alternatives. Unlike, say, a DEF heater, a balance shaft or intake manifold is part of the engine - and how many of those have you had to replace on the M272s that you like so much? More importantly, how many of the M272s and M276s that you've worked on have well over 250,000 miles and are still going strong?

Are the diesels the right choice for soccer moms in the USA that use them to do 20-minute grocery runs, keep putting in B20 diesel and only change the oil every 9,000 miles? Absolutely not. Are they the right choice for a vehicle that runs continuously for more than a couple of hours a day (or for that matter, 14 hours a day hauling parts) or for towing a trailer? You bet they are. If you are using the wrong tool for the job (or are using it incorrectly), it's not the tool's fault - it is yours, but you seem to be completely oblivious of that and are instead bashing the engine instead of those that are misusing it or not looking after it the way they should.

Anyway - it is apparent that you don't understand what the causes of any of the reported issues with the OM642 are and that we're not even close to having a meaningful discussion of any sort on the subject, so I guess we'll just have to disagree on this one. Thanks for your valuable input.