I know there has been a lot said on the subject of blow by but from what I've read most members seem to be experiencing noticeable blow-by with high mileage cars. My 240 only has 125K and when I do the oil cap test she dances all over the place rather violently. Also I've noticed that the air filter element which I changed is stained with oil and that sometimes I'll even notice a bit of oil has oozed out onto the hood and headlights by the air intake. She starts easily down to 20F but any colder and I usually like to plug her in to preserve the starter. Also, not sure if this is connected, after warming the car up in the drive on cold mornings there is always a big black sooty deposit in the snow right under the tailpipe. On the plus side my oil consumption seems negligible. With such low mileage is this normal or do I have problems?

What year is it? Any chance it has the early vacuum pump with a failed diaphragm which puts oil into the air filter assembly?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Could the vent tube be blocked off enough to be restrictive? If you're really worried about it, do a compression test. What kind of oil cap do you have, by chance? A flimsy plastic one would probably dance more.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

There nothing that isn't really invasive that you can do, and if it starts down into the 20's and doesn't use oil, who cares what the cap does!!
Also, you can't trust the odometer on these cars with such a high percentage of failures with the pot metal gear. Not to mention how easy the cluster can be swapped out.
Just enjoy what you got and don't worry. Would be prudent to verify the correct operation of the vacuum pump. Without a year given on your 240 we have no idea knowing which style you might have. But the older style will rupture a diaphragm and coat the air cleaner, but that would also show up as oil consumption, so that is unlikely.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

oops! It's an 83 4spd. By the way how do I go about listing my cars under my text like everyone else? And yes I do have a plastic cap. Are the metal ones significantly heavier? I'm just wondering if this is normal for a car with such low mileage.

Wow I hadn't even considered the mileage not being accurate. I guess I'm a bit naive. Especially since i know how easily the cluster is swapped out. Never considered it. So a compression test would be the best course to determine my motor's health.

No, your car starting down in the low 20's and not consuming oil is the best way to determine health.
Start worrying about other things.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

My '77 240 did and does the same thing 14 years later! It had 130,00 when I bought it. Has almost 150,000mi now. Don't worry about it.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Click on "User CP" in the blue bar above.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Guess I'll let this one go thanks everyone for your invaluable council.

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83 240D--125k (Lily)
87 Toyota 4X4 Pickup--90K
71 Triumph TR6C--13K (Rudy)
75 Puch

of course Jimmy lives in texas what does he know about 20 degrees

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commercial fisherman diesel in my blood in my boats trucks and Dear old Dad has had me drivin them since i got my first license in 1968
1986 300 SDL 427654
1999 Chevy Crew Cab Dually 225423
1986 300 SDL 287000 Dad's
1987 190 Turbo 158000 Mom's (my inheritance)

My cap (plastic) has always danced a lot ever since I bought the car 71k ago....it still runs perfect despite this. Fires right up....even without a heater at -7F (coldest it got this year).....one glow cycle....8 seconds cranking, off I went. Blowby doesn't always mean a problem. The blowby it has now is actually a little less than it was before I put it on synthetic oil 53k ago.....

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

There is no set mileage for engine wear! There are so many variables that effect engine life, they are too numerous to list.

With a diesel, as long as it will start and run and you can carry enough oil with you to get where you need to go, DRIVE IT! Unlike a gas engine, a diesel with worn pistons/rings/cylinders has no ill effects. You won't burn valves and you won't foul spark plugs.

Enjoy!

I wouldn't worry about it either - how does it idle? Smoothly? If not, maybe you need motor mounts - my theory being that the cap dances because the motor is sitting on collapsed mounts.

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- Brian


1989 500SEL Euro
1966 250SE Cabriolet
1958 BMW Isetta 600

My criteria for the oil cap test is, can you feel a real resistance when you put the cap back on because of the rush of blow-by? If not, it is not serious. You will always have the cap dancing if you leave it lying over the filler hole - the engine vibration and the normal pumping action of the pistons makes it impossible not to have some cap reaction. Another test is to just observe the blow-by. It is normal to have some gasses and oil mist escape. It is abnormal to have the quantity of gasses and ejecta look like a steam engine stack.

Overfilling the engine with oil is a common cause of excess oil in the intake. Too much oil and the crank becomes an industrial Kitchen Aid mixer, and the oil gets beaten into a frappe of blow-by and oil foam. This stuff will make its way to the intake and make a mess.

Like others have said, if it starts and runs, drive it. And, I am sure doing a compression test will generate an whole new round of concerns with questions that have meaningless answers if the car starts in cold weather and runs fine.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)