High oil consumption and smokey exhaust.

Contest1 said:
Further investigation has thrown up two issues.
I decided to check the reduction valve. I expected the spring chamber to be full of oil but it was dry. Gave the engine a few turns by hand a oil started coming through as you would expect.
After reassembly still smokey, gray white with no oil scum on the water. Small oil leak at the closure plate probably indicates its now operating operating correctly.
Took off the rocker cover to check clearances and noticed that the decompression bar does not depress the back exhaust valve. The tappet operates it OK but the when the decompression lever is moved away from the ground flat it dose not depress the valve. Very odd. The tappet clearence is OK at 30mm. Could this valve be failing to close fully.? Further investigation needed??
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0.3mm hopefully?

Richard
 
lw395 said:
Half a litre an hour of sump oil is a helluva lot.
It is seriously near running on burning the sump oil, which is a runaway condition which will rev your engine to destruction.
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Never experienced a runaway but I have been advised if this happens. Decompress the engine and if you are quick enough, you may just save the day.

All sounds a bit hairy to me!

Would be really interested to hear what the problem is and the solution.:encouragement:
 
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Tomahawk said:
What colour is the smoke?

If white, it would indicate oil getting into the exhaust and simply vaporising which would indicate leaking exhaust valve guides. Open the exhaust just before where it joins the sea water pipe.. If it is full of oil... you have found the culprit.. Also look at the exhaust water .. is it very oily leaving a pronounced smear on the water? .. again a symptom of unburned oil in the exhaust.
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Toma,

I have 'white' vapour from an old MD11c.
It runs ok, but I have been trying to diagnose it for a while, with some kind help on this forum.

I suspect unburnt fuel or oil, but had not looked into the valve guides as a problem.
I've had the heads off, and there is negligible play, so didnt replace.

But your exhaust water comment is interesting.
I have collected in a bucket.
Rather than a smear on top, there are (very few and very small) blobs of oil/fuel, but black.
Any thoughts on that??
 
What colour is the smoke?

If white, it would indicate oil getting into the exhaust and simply vaporising which would indicate leaking exhaust valve guides. Open the exhaust just before where it joins the sea water pipe.. If it is full of oil... you have found the culprit.. Also look at the exhaust water .. is it very oily leaving a pronounced smear on the water? .. again a symptom of unburned oil in the exhaust.
Toma,
Checked out the exhaust chamber after a short run. Plenty of unburnt oil in the exhaust chamber.
Again checked th clearence on the far exhaust valve. Still at 03mm.
Yet the decompression bar does not open it.
Looks like the valve is not fully seated??
 
If the valve wasn't seated it wouldn't run on that cylinder. Is the 5w30 oil that you have in the engine fully synthetic or mineral. If you have been using fully synthetic since the rebuild it will prevent the rings from bedding in properly. I would be using 15w40 or 20w50 mineral oil and see how the engine performs.
 
black mercury said:
If the valve wasn't seated it wouldn't run on that cylinder. Is the 5w30 oil that you have in the engine fully synthetic or mineral. If you have been using fully synthetic since the rebuild it will prevent the rings from bedding in properly. I would be using 15w40 or 20w50 mineral oil and see how the engine performs.
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Iv been using 10w 40 mineral oil since the rebuild.
Following your suggestion that it couldn't on both cylinders if the exhaust valve wasn't seated I used the decompression lever and definitely it's continues to chug away with the number one exhaust held open.
I'm still puzzled as to why the decompression bar fails to make contact with the no 2 exhaust valve
And were is the black unburnt oil in the exhaust port coming from??
 
Ok, I misread your original post, mineral oil is perfect, but still worth trying a 20w50. Regarding the valve seating, I meant seating on the exhaust seat in the head which it clearly is. I wouldn't worry about the decompressor bar, it won't cause you any problems. How many hours has engine run since rebuild and did it use oil before the rebuild? Were the cylinder bores honed before the pistons were fitted?
 
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