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Old 03-08-2006, 13:49   #1
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Oil Consumption

Some background,

I run an older Ford "Lehman" type 6 cylinder diesel in a steel 50 foot ketch. The nominal horsepower is 120. The engine hours are approx 4000.

I have replaced the head gasket, valve springs, ground the valves, new injectors and serviced the injection pump, whew !! The re assembly was done with a good quality torque wrench following the correct bolt tightening sequence, they were also checked after 20 hours.

I would greatly appreciate any input re the expected oil consumption of this engine under continuous use at say 1800 rpm which results in a speed of 6 knots. The actual consumption is approx a litre every 24 hours. There is no visible smoke, there is no water in the oil and no external leaks on the engine.

Thanks
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Old 03-08-2006, 14:08   #2
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And you see no oil on the surface of the water from the exhaust outlet????
1lt/24hrs is a little high, although so is 4000hrs. I am not sure the usage is high compared to the probable engine wear. But am am surprised you are not seeing tell tale signs like blue colour in the exhaust smoke.
Possible causes dues to engine wear will be, oil getting past the rings and oil seeping past the valve guides. It is the only way an engine can "burn" oil without it being really obviouse such as leaks etc.
The only other place would be a breather back into the intake, but this results in big billows of black smoke and a very horrible detonation noise and the engine is basicaly shot.
Ring wear could be detected via a leakdown test. I suggest you carry out a leakdown test and see what cylinder wear you may have. By the way, what did the cylinders look like when you had the head off???
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Old 03-08-2006, 14:29   #3
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The head, cylinders and the pistons looked in great shape, there was no visible scoring etc. I think my main concern is that I have some wear in the bearings but I don't have a visibly smoking exhaust but I suppose there could be a blue tinge... maybe.

The reason for the upper engine rebuild started off due to a lack of power under load and what appeared to be unburnt fuel on the surface of the water. The injectors were in bad shape when I pulled them, which would account for the poor combustion. Following this service there was an obvious increase in power and the unburnt fuel issue was resolved.

I am still concerned about the oil consumption but with an "older" engine I suppose it should be expected!
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Old 03-08-2006, 18:32   #4
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You two know more about this than I but I've got to ask, where is that oil going? If you can't see it burning and you can't see that it is leaking, where else can it be going? Transmission, cooling?
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Old 03-08-2006, 19:03   #5
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The best way i've found for checking smoke color, is to run the engine at night and shine a flashlight thru it. My vote is for rings.
How was the engine starting? did it take a long time cranking? did this improve with the top-end job?
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Old 03-08-2006, 22:22   #6
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The engine definately started better/quicker after the work I did but the pristine new injectors could account for that. I had the old ones rebuilt as spares and as yet have not needed to use them. I think that the suggestion to do a leak down test is a good idea and will do this in the next month or two and report back.
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Old 04-08-2006, 13:29   #7
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John it could very well be your piston rings.you can also do a compression test,that will tell you really what's going on.also check your air filter if you do have one,that can also affect your oil consumption.JC.
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Old 04-08-2006, 16:09   #8
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A further question John, does this Ford have the harden steel cylinder lining inserts or the cast lining inserts? the harden steel has a lot of chrome in the metal and these inserts are higly suseptible to glazing. If the cylinder wall looked like a mirror or lovely chrome finish, then that is the result of excessive polishing or "Glazing" of the bore. This will cause excessive oil burning. It takes little oil to bypass the rings to add up to several ltrs in a 24hr preiod. You may notice it as a light bluish tinge in the exhaust.
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Old 04-08-2006, 16:43   #9
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John, another vote for a leakdown/compression test. One liter in 24 hours would be similar to one quart in one thousand road miles. Mercedes used to call that normal--but they intentionally allowed oil to get past the rings. Detroit has never called that kind of consumption normal.

The other possibility is that it is leaking past a main bearing in the engine, but then eventually it would be getting into the bilge or into whatever is beneath your engine.

One old way to check for oil in the exhaust is to hold a white cloth or paper towel over the exhaust for a few minutes. When you take it away, if there was oil in the exhaust, there will be some oil stain on the cloth. Sometimes easier to smell, or to see by spraying water on it and seeing the "circle" where the oil-fogged cloth won't wet out.
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Old 04-08-2006, 16:57   #10
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You need to do a compression test first and then go from there....anything else right now is speculation.

There are several means for loosing oil, start with compression. Worn rings can account for oil loss even though you may not see it out the exhaust.

How long have you been keeper of the engine? Seasonal boater? And how long between oil changes?
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Old 04-08-2006, 22:03   #11
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Rings Rings Rings

If you have had the valves done.....the next logical place for oil to go is past the rings.

Is the engine hard to start? Have you EVER used ETHER?

When I survey engine, I have oil samples tested. I don't know where you are, If you send me an e-mail perhaps I can find someone close to you who can give you a kit to take the sample.

Also, if you have a compression test done make sure it is done with
a DIESEL ENGINE COMPRESSION TESTER. You can't get it at your auto parts store.
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Old 05-08-2006, 22:44   #12
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Thanks for all the great suggestions, everyones coments are much appreciated. The oil consumtion of a litre every 24 hours was during a season in the S Pacifc when the engine was in regular use.

I am not sure what the cylinder linings are made of ?

What is the significance of using ether, I have not used it but I do know people who use it on their engines. Following the engine service and large crank battery the engine starts within a few seconds.
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Old 06-08-2006, 05:59   #13
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Quote:
Originally Posted by JohnB
Thanks for all the great suggestions, everyones comments are much appreciated. The oil consumption of a litre every 24 hours was during a season in the SPacifc when the engine was in regular use.

I am not sure what the cylinder linings are made of ?

What is the significance of using ether, I have not used it but I do know people who use it on their engines. Following the engine service and large crank battery the engine starts within a few seconds.
Ether, better known as starting fluid, can proove catastrophic to a diesel engine if too much is sprayed into the intake. I have used it a few times but only as a last resort and only in tiny amounts. You shouldn't need to use ether at all if your engine is within specs such as with compression. Also, most diesel engines use glow plugs and if one or more glow plugs are burned out they will be difficult to start. Using an ohms meter, you can test each gp. If a gp shows no reading it's junk. Generally, you should see anywhere between 01 to 08 on your meter for most small diesel engines, if the gp is good. Glow plugs and the glow plug relay don't last forever, check both.
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Old 06-08-2006, 10:55   #14
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Well, to answer yer question about the oil consumption being "normal" or not:

I have an old Perkins 4-108 with at least 7000 hours on it and I use about one quart (liter) every 50 hours or so.

Some of it leaks out at the aft bearing, but it seems to seal up a bit when I use the boat frequently.

Some color to the exhaust when accelerating to high power, but that is probably unburned fuel.

Just crossing my fingers that this old 1979 vintage engine will keep going strong.

Don't think your 1 liter per every 24 hours of running time is too high, considering the age and hours of the engine.
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Old 06-08-2006, 11:22   #15
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John, ether is a mixed blessing. A good thing, because it is (IIRC) way more volatile than gasoline and crosses the line between "combustible" and "explosive". Think what happens if you put gasoline in a diesel engine (BOOM) and then realize the ether goes boom with much less provocation.<G> I'm sure that picture isn't quite right but the same easy BOOM is what makes ether a good way to start a reluctant engine, you'll get the fast BOOM but the rings and cylinder heads might not like it on a regular basis, and I'd give you odds it scours the oil off the cylinder walls must faster than diesel fuel would.

You know diesels, they'll try to eat anything that you feed 'em. Just like dogs, and you know what happens when a dog eats something it shouldn't have.<G>
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