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.

__________________
"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

I’m a big fan of oil separators. My theory is if there’s less oil coming into the intake from the breather circuit, there’s less oil or gunk up the intake and get into the combustion chamber.

The best way to remove carbon IMHO is having an engine that burns clean. So I drive my engine clean by using a stock injector pop setting, stock timing and I limit oil vapor from getting back into the intake using a separator. I was chasing an engine shake and I finally concluded I had to reduce the oil vapor going into the intake.

Not so sure about diesels (that run lean Lambda) but on gas cars extra fuel or oil = more carbon deposit. If you get the mixtures back to normal the carbon will combust…slowly, eventually. It’s just simple thermodynamics you need excess oxygen to combust away carbon and it won’t happen with excess fuel. It has taken a couple of years for me to drive my SD clean. Before that I tried all kinds of solvent soaks and sprays without much luck. Once I stopped pouring a 1/4 cup of oil a month into my intake via the breather it has really transformed itself. But it didn’t happen overnight.

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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, That is great advice, it makes total sense and it was very well stated. Thanks!

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

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.

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

Who makes engine restore?

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.