1984 Mercedes 300D-Turbodiesel All service records and books from Day One. Lapis blue/palomino interior;new transmission plus many extras.(read Extra Text)
Additional Text Always garaged. All new front end, new rear axle, new transmission, new carpet. Reciepts and stamped service books by Mercedes mechanic. Original mag wheels, PIAA headlights, am/fm/cd with Boston Acoustic speakers. 276 thousand highway miles.

Here's what I know from talking to this guy. He's owned MB Diesels for 25 years. He bought a mint sd with 100k, and is now selling this. He said transmission was 2k to replace. Car needs nothing but paint. He was going to keep it, but found his sd and snatched it. Compression he says is between 300 and 310 psi on 4 cylinders, with one cylinder at 290.

My question is what life should be left on this engine if I take these compression numbers as valid, or is strictly compression not enough to go on? I forgot to ask about oil consumption.

I'll take a stab at your question. The numbers look acceptable to me. I would also check the blowby. Remove the oil fill cap when warm and see what comes out. Little puffs of smoke=ok. Puffs like a steam locomotive=not so good.

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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

The compression numbers are not bad at all. The "take off the 710 cap and look for smoke test" is not very meaningful unless you've seen it on other engines of known condition. It's kind of hard to describe in text. The compression check is much more meaningful.

Good luck,

Larry:
You're right about that blowby test. I have seen vastly different amounts of pressure and smoke come out of different engines but I'm not sure how those engines measured up in other tests. Perhaps we should try to quantify it. The 'number of seconds it takes for the engine to shut down with blowby tube plugged' test is too relative to the condition of seals in the engine. Could we do it by putting a standard ziplock one gallon storage bag over the oil fill and counting the number of seconds necessary to inflate it and then compare the numbers on engines known to be good or bad according to other tests?

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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

Well I'm sure there is a way to quantify it but the gallon baggie test might not be the way to go. My car would fill that bag in less than 2 seconds. It huffs pretty good in a nice rythmic fashion when I remove the oil cap, engine hot at idle. I've heard thats not a good sign yet I get 26 mpg on average, engine doesn't leak a drop of oil at any time, acceleration is excellent, and it starts within 2 seconds of cranking every time. By the standards of the blowby test one might consider this engine very tired yet I can't see how that is possible at only 169,000 miles and such a strong runner.

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Orland Park, IL
1985 300SD 215,000 miles

I would have to agree with Larry. Have two old MB diesels. The oldest one is a 78 300D with 351,500 miles. Pull the breather cap and it barely smokes at all. But compression is low, about 285 per cyl, and it does burn oil.
My 81 300SD has 214,000miles and throws a lot more out the blowby tube. Compression is high, at 400 to 410 per cyl, and it does not burn any oil. So I have doubts about that test, at least as a sole exam technique. Useful I am sure, but with these old diesels you need more information. I would try to get it away from the guy for an hour and drive it at 65 down the freeway. Check the oil level before and after. Should tell you more.