Sure you have other things to do but the valves could/should? be adjusted again in another 1K miles and until they hold their clearance. This is not uncommon for valves not adjusted for a long time.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Yup. I didn’t believe you when you told me a few years back. So I filled some jars with Marvel, diesel fuel, acetone, brake fluid, chem tool and then I dropped old valves in them. I checked them a few months later and the really hard carbon deposits were still there. The soaks may take off the oily sludge but that hard carbon needs to be chipped away.

Chemically carbon is just carbon. What is it going to dissolve into? More carbon? I guess it’s like taking a lump of coal and dipping it into some solvent thinking it’s going to turn into liquid. This does happen in nature but it takes a lot of pressure and heat about 10,000ft underground…and a million years.

That’s why I believe I’ve had really good luck burning it off slowly by running clean. There is the mechanical action of the engine firing and flexing the rings. There’s a lot of heat and enough oxygen to burn the carbon. When you fire a charcoal forge you need a lot of air to get the coals glowing bright and even then it takes time to burn away a lump of charcoal. It just glows and slowly disappears.

It’s kind of a race between how fast you deposit the carbon and how fast you get rid of it. If you overwhelm your engine’s ability to burn it off by dumping oil on top or from the bottom of the chamber it’s going to Coke up eventually. What better way to gunk it up than to add too much fuel or deplete oxygen?

I think as our cars wear they just are forced to eat more oil than they were designed to deal with and it overwhelms things…worn bores, pistons, rings, turbo seals, valve guide seals, valve cover baffles. It would have been interesting to see if a brand new OM617 powered Mercedes off the lot had oil snot all over its intake.

On these new GDI cars it just builds up in the intake. You can do a shell blast and clean it periodically which is a radical cleaning but over time it’ll just build up again and then you need to clean again. The average rate of deposit exceeds the average rate of removal and eventually you’re buried in carbon crap.

I am amazed how my car runs after a couple of years of driving it clean. Before I fixed my baffle in my valve cover and added a separator my turbine was just dripping with oil all the time. Now it’s mostly dry. My U tube doesn’t drip oil anymore either. The car had terrible shakes before but now it idles smooth - about twenty thousand miles after I fixed the oiling issue. It was a very slow process. The car also starts more easily.

I got this whole drive clean idea when I thought about reading plugs on my gasser bikes as a kid. If you run rich you get carbon buildup on the plug and the plan is to lean the mixture till the plugs look clean. But this tuning technique gets confused when your midrange mixture is rich but you’re idle mix is lean. You pull over, idle down, remove the plug and by the time you have the plug out it’s squeaky clean. Despite the fact you’re mixed rich. The lean idle cleans it up if you’re too slow chopping the throttle and killing the engine. This is how plug reading goes bad. I verified this with a wide band lambda meter. Without Lambda monitors in the exhaust you’ll totally miss the rich condition when reading the plugs because they clean themselves up naturally under the right air fuel ratio.

I think the same process happens on the average in our diesels. Our Lambda (air fuel ratio) varies widely during operation but on average it provides the correct balance of air and fuel to have a neutral carbon deposit rate. If rate in - rate out is not zero on average you’re gonna get buried in carbon eventually.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Ykobayashi again great info, keep the oil out of the intake right from the start!

Your theory also supports the concept of getting the engines up to full temp and running them hard to get the rings to flex.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer