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The carbon buildup on the intake values comes from oil blowback leaking past the piston rings which is evacuated from the combustion chamber and collected and recycled back into the intake air and the oil is then deposited and baked onto the stem part of the intake valve. With carburated and port injection engines, this part of the intake valve is washed clean of the oil and combusted along with the fuel mixture. I had a 2008 Lexus LS460 that had both port and DI in its V8 engine so the back side of the valves were washed part of the time when the port injection was computer selected. There are youtube videos that discuss this issue and different ways to clean the valves with blasting the valves with crushed walnut shells being the best solution presently offered.
The carbon buildup on the intake values comes from oil blowback leaking past the piston rings which is evacuated from the combustion chamber and collected and recycled back into the intake air and the oil is then deposited and baked onto the stem part of the intake valve. With carburated and port injection engines, this part of the intake valve is washed clean of the oil and combusted along with the fuel mixture. I had a 2008 Lexus LS460 that had both port and DI in its V8 engine so the back side of the valves were washed part of the time when the port injection was computer selected. There are youtube videos that discuss this issue and different ways to clean the valves with blasting the valves with crushed walnut shells being the best solution presently offered.
Yes, well aware of this. It's just a PITA to do, and it's not a cheap cleaning process either. There are other solutions as well which are not nearly as effective, but they can help.
The M276 engine has had timing chain tensioners and oiling issues since 2013. TSB LI05.10-P-056435. If not taken care of the end result is very expensive, as the oil pressure goes low in the main galleries and destroys the con rods and bearings. budget about $13K for a rebuild, If your are unlucky then the timing goes way off and the engine grenades itself
Main symptoms are clatter on start up that lasts about 20 sec.
It's important to use top tier gasoline, but again the idea that it will prevent carbon build-up is flawed. The consumer reports article showing the valve pictures is from port injection. The only way gasoline would come in contact with the valves in the DI Benz engines is blow-by, and the MSI (multi-spark injection) apparently cuts that possibility out.
Octane rating and whether or not a gasoline is top tier are unrelated.
Now it's 8/18/20, CRC came out with an Intake Valve cleaner with good success. I have done a lot of research regarding the carbon buildup on intake valves and injector nozzles. I have read this thread thoroughly and Lilbenz230 has an excellent understanding of the carbon buildup issue with DI engines. Quality of fuel has nothing to do with this issue. Top tier gas helps a cleaner engine but doe nothing to clean the intake valves since the fuel does not touch the valves in a DI engine, where as Top Tier gas does good job on Port Injection engines.
I plan to use the CRC cleaner since my E400 has about 30K miles.
E Coupe C207, ML W166, ML W164, Sprinter 1500/144, W111 SB220 Fintail(s), A5 chassis Beetle 5+5
Originally Posted by superangrypenguin
The comments about using top tier gas are asinine and quite frankly it reflects a poor understanding of how DI works. It helps (the fuel additives survive combustion for top tier gas so that may help clean intake valves (blowby) but it is not the solution)
Have there been pics taken of MB DI engines' intake valves? Without this, it's hard to say that the issue has been resolved. Most people can't tell if their engines have decreased HP after a few years due to DI and the carboning (is that a word?) of intake valves.
Has the reduction in flashpoint in oil due to DI stopped? Have people been posting UOA's of engine oils for MB DI engines?
Without solid information, we cannot say that the issue has been resolved.
Oh really, how about the valve overlap during VVT operation, when the fuel mix backs up over the intake valves? ...especially in Budak or Modified Miller Cycle engines.
E Coupe C207, ML W166, ML W164, Sprinter 1500/144, W111 SB220 Fintail(s), A5 chassis Beetle 5+5
If you want a clean engine and fuel system use a gallon or 2 of E85 in a tank. 2-cycle oil makes a great fuel additive too, at 500:1 or more. I buy it by the gallon at W*M for like $11
Agreed! In my country I use 100 octane, euro 6 petrol for my M276 engine. I'm thinking of also using that for my M272 vehicle as well. Also, try to avoid petrols with ethanol as this leads to carbon build up. The 100 octane petrol I'm using is ethanol free and is tagged as NEAT gasoline. Good luck.
I can't attest to the validity of the attached document only insofar as I sourced it from another thread on this site, and that it's very thorough, but it's describing the method MB uses for PCV oil control on the E400, and by extension the E450 engines:
"Two-stage engine ventilation system with rotating radial separation and downstream high-volume fine separation for optimum cleaning of the blow-by-gas"
It goes on to describe the use of a cam-driven centrifugal prefilter and fine oil particle separation chamber, though only to the effect of decreasing engine emissions and lowering oil consumption. It seems to me that this entire system is providing the effect an aftermarket oil catch can/ air-oil-separator would, something that's talked about heavily on the VW forums in TFSI threads. A few members have mentioned other makes having well documented coking issues with their DI engines, but the general consensus is that MB has found a way to mitigate it. At least delay the buildup enough to guarantee the cars are out of warranty before it happens. I'm not savvy on whether or not the 3.5L NA 276 engines use such a system, as all the research I'd done before I bought my car was into the turbocharged engine after being burned by goopy intakes valves on previous VW's of mine. This paper also mentions, in addition to the multiple sparks per cycle, that multiple injections per cycle, up to 5, can occur. There's been plenty of debate in this thread about the validity of claims that top tier fuel is a way to save your engine from looking like crud, and while I agree that it's easy insurance against HPFP and other fuel system failures down the line, it's not going to do hardly anything to help keep your valves clean in a DI engine. But after reading about the injection method this engine uses, which I imagine WOULD carry over to the NA engines, and other thoughts about chamber and port design, would it be possible that MB uses an injection or two during each cycle while the intake valve is in it's fully open position to actually spray the valve with some fuel? This could be a factor in why we haven't heard much in the way of the NA engines gathering much crud on their valves either. Spitballing here, but just a thought.
Anyway, attached document was a part of the deciding evidence that led to me buying my 18 E400 wagon, along with several other threads on this forum. First post including picture of wagon doing wagon things
08-23-2018, 04:35 PM
