Oil Consumption

I know this is a Mercedes auto forum but I need some advice on a 240D in a marine application. We just purchased our boat with a marinized 240D. We were told that engine is a fresh rebuild with 10 hours but on the way down
to south FLorida we burned about a quart of oil every 4 hours. No major leaks anywhere and the engine sounds good. Plenty of power but alot of oil consumption. Any ideas? I am wondering if the engine was properly broke in and if the rings are seated, Thanks JAB
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On Sun, 03 Apr 2005 08:49:45 -0400, Tom Matsoukas wrote:

This sounds majorly wrong - broken in or not, this is roughly equivalent to 3 or so days of highway driving draining all the oil from the car - which is well, did I say majorly wrong?
I suspect, while being a total land-lubber, that there is a universal truth here - used boat salesmen are just nautical used car salesmen. You mentioned Florida - not that it matters, but at least there is some press covering Florida and boating lemon laws - but it's not real encouraging.
http://www.boatus.com/consumer/art3.asp http://www.findarticles.com/p/articles/mi_m0BQK/is_2_9/ai_114604627
The other universal truth may be this - not any old machine shop can properly rebuild the MB diesels - in fact, has ANYONE out there had a positive rebuild experience on one of the diesel engines? I've heard a ton of scary stories. Is anyone doing it right?
Best of luck - I'd try the BBB, your attorney, and lots of letters to any Florida legislators you can think of. The good news is that you can still find these engines in "gently used" condition in vehicles that have suffered some degree of body trauma - so all is not lost.
Conrad
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The engine isn't properly "broke in" at 10 hours. A marine application is a hard (constant load) situation for a newly rebuilt motor. Sounds like the rings have not seated and may not seat at all without another teardown to find out why. Without a compression test it's pretty hard to speculate here. Have a good diesel mechanic (MB or other) have a look and try and ascertain the problem if there even is one.
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An auto engine will use lube oil when it's driven hard. Automotive diesels are high speed diesels whereas most marine diesels are relatively low speed engines due to their constant speed use. Marine use is substantially different from automotive use - marine use is almost always constant speed and often at lower than designed engine operating temperature.
IMHO, this little 76 HP high speed diesel engine should not be run at constant speed above say 70% or max 75% of its maximum RPM (I don't know the 240D maximum load rpm, say it's 4,500 rpm) then 70% is 3,150 rpm and 80% is 3,375 rpm.
These engines are designed to run at 80 degrees C. or about 175 degrees F.; be sure it's running at that temperature.
A compression check will confirm the engine's internal condition better than anything else short of disassembly.
New car break in used to be about 2,000 miles of VARIED driving. At say, a 30 mph average, that's about 67 hours of running, not 10 hours of marine use.
If it were my engine I'd use Diesel grade SAE 20-50 oil - don't use gas engine oils.
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Have a friend who put a used 4-cyl MB diesel in his 40-ft trimaran and it worked out beautifully. Only problem was the hardest part to get to on his installation was the starter. Guess what gave him fits?
Anyway, a rebuilt engine will take some break in but stationary diesels are broken in running at constant speeds and I'm told this is preferable to variable rpms. A diesel of any make, certainly one of the bullet-proof 240Ds, should work fine. I'd have the compression checked both "wet" and "dry". A mechanic will know how to do this on your engine.
On gasoline engines you remove all of the spark plugs and check the compression of each cylinder. On diesels you remove either the injectors or glow plugs. After each cylinder has been checked and the psi written down, do the same again. However, this time put two or three "squirts" of oil in each cylinder and see if the compression increases measurably. Be sure to inject oil in the individual cylinder you're getting ready to check, not all of them at the same time. Doing so will force a lot of the oil out the injector port.
The reason you do this is that the oil will temporarily seal any leaking rings and sometimes leaking valves. However, in a rebuild any compression loss will almost certainly be rings.
As far as engine oil is concerned don't use 20-50 unless it is recommended for diesels. This is normally reserved for engines with a lot of wear. The preferred oil is 15-40 such as that offered by Chevron. Although the viscosity is slightly less when the engine is at operating temperature, it is designed for more stressful conditions, such as a diesel.
Good luck!
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On Mon, 04 Apr 2005 04:18:06 +0000, Ernie Sparks wrote:

Just had one other thought - even if you get great compression readings on a compression test, it's still possible that the rebuilders did poor (or no) work on the valve guides. A good compression reading indicates that the piston/rings are sealing the combustion chamber at the bottom, and that the valves are sealing against the valve seat - but bad valve guides will still cause you to lose oil.
I still contend that regardless of the usage, steady rpm marine use, or cruising up I-95, that this is WAY too much oil to be losing.
Conrad
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No argument about that. The oil consumption is way to high. Intake valve guides/seals are a good place to look. You can sometimes determine if this is the problem during a throttle-down situation. I'd rev the engine as high as you feel comfortable with and then fully depress the "stop" lever. Don't know if you get the same results as with a gasoline engine but blue smoke should exit the exhaust if you're drawing engine oil past the guides. I know that on my 240D if I just get in and immediately crank the cold engine without waiting for a glow plug warm up, blue smoke will exit the exhaust....all that unburned diesel fuel. Same with engine oil.
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there are no throttle plates so it will not pull much of a vacuum shutting down.
when this is done with a gas car the plates close and a great vacuum is created between the throttle plates and the cylinders.<valve guides been in the middle>
that is why trucks can use a jake brake <engine compression> because they are full intake flowing and the jake brake cuts off the exhaust.
BUT i could be wrong
the case, minus a few cans!
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Thanks everyone for the excellent feedback! We did a C-check and discovered very weak pressures in all cylinders. When we checked blow-by and blocked off the crankcase vent we got massive oil geyser out of the dipstick tube. Along with the oil came many small chunks of metal. My guess is that a oil ring or two gave way. At any rate I am in the market for a reman short block. Any leads on good sources would be appreciated. Thanks, JAB

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See: http://www.mercedesengines.net /
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Wow! They charge twice as much for a shortblock, as I paid for a whole car with an excellent engine...
I would recommend finding a good running car with some body damage or rust...
Marty
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Tom Matsoukas wrote:

there is a 240d motor on e-bay
ngines & Components > Complete Engines         Mercedes Diesel Motor~150k miles~240D~1975~RUNS~4 cyl    em number: 7966508345    
J.
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On 2005-04-07 08:19:52 -0700, Into the living sea of waking dreams

Don't buy an engine on EBAY! You can't see it or hear it run! Unless you are collecting blown motors that is.
Marty
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