Hi,

I adjusted my valves recently on my newly acquired 1980 240d 4 speed and noticed 3 valves were extremely tight.

The car is fairly low mileage with around 120K miles.

I notice a slight dance of my oil cap at idle, although it got better after I adjusted the valves. It is not terrible or overly concerning to me because it starts right up and stops the same way. Runs with plenty of power.

However, I am thinking that the car was driven awhile with the tight valves and was wondering if there is anything that I could add to the oil that may help burn off carbon that may be causing the oil cap dance (this is my 3rd diesel).

I want to get ahead of this to keep the engine healthy just in case there is any buildup of carbon.

Thanks.

go to youtube.com and watch Kent's videos concerning the Liqui-Moly products. He explains the Liqui-Moly products in an easy to understand way that makes sense for high mileage engines. Here's one although there are other videos where he goes into it in more detail.




https://www.youtube.com/watch?v=rh0PtXwZo_Q

Re-adjust the valves in about 1K miles, when they are far out-of-adjustment it may take 2-3 adjustments to get them to maintain a clearance.

Get it hot and run it hard, full throttle uphill and let it coast in gear downhill and repeat several times to work the rings back and forth in the piston grooves.

Do 2-3 short interval oil changes e.g., 1k miles on a hot engine, obviously be careful to avoid burns.

If concerned about carbon build up use a borescope to look down the intake runners OR remove, clean and re-gasket the intake. It isn't that difficult on a 240D. With the intake off you'll have clear access to the valve stem area.

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

Add Seafoam or Marvel Mystery Oil to the oil just before a change, rev it up and down at idle or drive it hard for a short distance then dump the oil, don't leave these in your oil permanently as they thin it out. They're more for cleaning sticky lifters but they can help free up rings too.

Full synthetic oil has more detergent action and lubricity, it can free up rings and clean valve guides to the point where an older gas engine will puff blue smoke on startup. Ask me why my quad puffs blue smoke now... there has always been debate on whether you should run synthetic or not and probably always will be. I have overly light synthetic in my 2.5L right now as a flush.

Liqui-Moly Diesel Purge really works on injectors. I'm always skeptical of these products but this one really works. Smoothed out the idle a lot and really reduced nailing and clatter. Run it straight from the bottle into the lift pump, there is a video on Youtube showing how. Make sure you have a primary filter inline as junk will be coming out.

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1993 300D 2.5L Turbo

I will add Engine-restore reduced some of my blowby. other people have had good luck with it as well.

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1977 240D auto w/OM616.916 engine
2005 Matrix 5spd
2006 Prius

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I wouldn't add Engine-restore until after running it hard and doing hot, short interval oil changes. I think I'd try synthetic Mobil 1 or the like for the cleanup. I'd also avoid any engine flush products due to it having a rope type rear main seal, old oil cooler hoses and an oil cooler without a drain.

The Engine-restore could go in after the clean-up.

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

Amen on the Mobil 1 and think twice about that other stuff
Now I don’t want start a dreaded oil thread but I’ve used it in both my 85sd’s for years. One with 370,000 and the other 171.000. Previous owner used Valvoline Advanced Synthetic so can’t complain because that engine is tight he really maintained it well. (He raced stock cars).
My Pop, when he picked an old diesel ( truck, dozer, tractor,etc,) that been sitting he would drain and fill will cheaper oil brand and mix tranny fluid, it’s a good detergent and run it drive it drain and fill repeat.
I think about him every time I open the hood and his old tool box.
greazer2b

I wouldn't run it hard with any cleansing agent in the oil. Diesels place a very heavy load on connecting rod bearings, I'd be concerned about damaging a bearing due to reduced lubricity from the cleansing agent.

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

Who makes engine restore?

Yes maybe I should have been more specific not to run it for long and not to add much. In my opinion the main point of these solvents is to thin the oil, fluidize sludge and get it to drain out effectively. They're not a regular maintenance thing, but something to use on a dirty, sludgy engine.

So I mean to add a couple ounces, rip it up and down the block to flush it through the passages, and dump the oil.

Totally agree on the oil separator. One of the first things I did to my oil-soaked 2.5 turbo was add both a catch can and the Dorman 46065 vent valve that was recommended on this forum. That valve prevents the turbo from drawing a vacuum in the crankcase, and really cuts down the oil vapour. Only a few drops of oil in the catch can since installing the 46065.

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1993 300D 2.5L Turbo

Nothing will dissolve carbon.

You may be able to soften it with Marvel Mystery Oil but not dissolving it, say try to unstuck piston rings. You can only scrape carbon off mechanically.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

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1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

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.

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

Run some steam through from a garment cleaner or wallpaper steamer.
I would do this on my om603 that I ran on vegetable oil every oil change.
I would remove air filter lid and element and then just position the steam pipe just outside of each cylinder inlet in turn for ten minutes at normal idle speed , it would suck in what steam it wanted and was not forced to much at once so no need to have it at say 2k revs
About a litre of water used as steam for each cylinder and this will clean the complete cylinder and piston rings up .. think of how clean a cylinder is when a head gasket fails.
It works and costs nothing apart from time

OK.

I drove the car 1K miles from the initial valve adjustment and oil change.

Today I changed the oil again and did another valve adjustment. 2 of my exhaust valves had tightened up and needed to be readjusted, everything else maintained its clearance.