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Prime Suspect

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Nov 22, 2008
3,563
Endeavour 32 Portland, Maine
When I had my starter and alternator overhauled last spring, both were found soaked with oil inside that clearly came from the crankcase breather tube that ended right above them near the air intake.

On the advice of the person who knows more about boat systems than anyone I've met, I installed an oil / air separator in the breather line.



The separator collected about as much oil as you see in the picture over the first couple thousand miles. I noticed that it has been filling faster in the past couple of months but I've been operating pretty much as a powerboat.

During the oil change one day of operation before the bleed out, I found the separator filled about half way up and drained it. I've also noticed that the dipstick has been coated with oil all the way up when I pull it after a run. If I wipe it off and reinsert it, it reads properly. This is new so something seems to have been changing in the engine.

I looked at the breather last night and saw that the filter element was oil soaked. I disconnected the breather line from the block last night and tried to blow through it. I could barely get air to move, clearly over the 3 psi limit of most oil seals. Strangely, when I repeated the test this morning, air whistles through effortlessly.

The big question now may be how much damage has been done to the seals or other engine components.
 
Feb 6, 1998
11,096
Canadian Sailcraft 36T Casco Bay, ME
When I had my starter and alternator overhauled last spring, both were found soaked with oil inside that clearly came from the crankcase breather tube that ended right above them near the air intake.

On the advice of the person who knows more about boat systems than anyone I've met, I installed an oil / air separator in the breather line.



The separator collected about as much oil as you see in the picture over the first couple thousand miles. I noticed that it has been filling faster in the past couple of months but I've been operating pretty much as a powerboat.

During the oil change one day of operation before the bleed out, I found the separator filled about half way up and drained it. I've also noticed that the dipstick has been coated with oil all the way up when I pull it after a run. If I wipe it off and reinsert it, it reads properly. This is new so something seems to have been changing in the engine.

I looked at the breather last night and saw that the filter element was oil soaked. I disconnected the breather line from the block last night and tried to blow through it. I could barely get air to move, clearly over the 3 psi limit of most oil seals. Strangely, when I repeated the test this morning, air whistles through effortlessly.

The big question now may be how much damage has been done to the seals or other engine components.
Roger,

As a little experiment I just blew into my Ritchie pressure tester for plumbing systems, tanks etc.. The scale is easy to read. Blowing as hard as I could, before ripping out my cheeks,;) the most pressure I can develop is about 1 pound perhaps 1.2 as a "peak".. If you were still "blowing though" I would have to guess it was certainly less that 1 pound...

3 PSI is a lot of pressure..
 
Nov 22, 2008
3,563
Endeavour 32 Portland, Maine
If you were still "blowing though" I would have to guess it was certainly less that 1 pound...
Last night was about the minimum passage that I could detect as a decrease in the pressure on my cheeks. I couldn't really tell that air was flowing.

This morning, I could hear air whistling and it was almost like blowing into a long open tube. I wonder what could have changed overnight?

Maybe the disconnecting and connecting dislodged something that had gotten into the hose. Me engine can't be drained and I have to pump oil out through the dipstick so there could be some sludge in the bottom of the oil pan.
 
Nov 6, 2006
8,508
Hunter 34 Mandeville Louisiana
Looking at the drawings, I don't see anything that would be damaged by a little over-pressure. If the other seals and gaskets aren't leaking, everything should be fine.. except for the big leak. If you've replaced the diaphragm lift pump with an electric (? seems like I remember you did) then there would not have been fuel disruption on crankcase over-pressure.. After thinking on the pressure, the lower part of the lift pump diaphragm would see the high crankcase pressure and the spring may not have been able to push it back down. Your dipstick observations sound like over-pressure because the dipstick tube bottom is below the oil level.. Any chance that the oil was running down the OD of the tube and drooling back so it looked like it was collecting under the flywheel? High crankcase pressure would have blown the oil up the tube, wetting the dipstick all the way up as you noted.. and after the pressure is released, the oil level would show true.
The breather tube exit should be connected to the intake manifold ?? drawing shows tube from cover over the injection pump going to a nipple under the intake manifold .. so the vapors get consumed..and the crankcase vented to a smidge below atmos press.. ??
 
Nov 6, 2006
8,508
Hunter 34 Mandeville Louisiana
Liquid oil slowly draining out of those teeny 5 micron pores could explain the difference
 
Nov 6, 2006
8,508
Hunter 34 Mandeville Louisiana
Feed pump pressure of the diaphragm pump is specified at 1.4 psi.. I don't know what the diaphragm balance looks like .... I am convinced that your dipstick tube is the culprit ... oil was being pushed up and out because of the high crankcase pressure .. would take only about 0.35 PSI to do that .. More plausible on the separator..
 
Feb 4, 2005
524
Catalina C-30 Mattituck, NY
Roger -

Have you tried calling Mac Boring Tech support with this? 908-964-0700I believe is the main number. Yrs back - I had an odd issue with my Yanmar YSM and Bob was a tech expert I spoke to that walked me through various trouble-shooting scenarios around a remedy for the issue I was experiencing. Give them a call and see if they can help.

- Rob
 
Sep 25, 2008
1,052
CS 30 Toronto
"On the advice of the person who knows more about boat systems than anyone I've met, I installed an oil / air separator in the breather line. "

The question is why should there be oil in the breather tube in the first place. You should not install an oil / air separator as advised by the person. You should find out why is there oil in the breather tube.

The breather tube is equivalent to automobile PCV (positive crankcase ventilator) system. All engine leak a little; via the valve sleeve, ring etc. The gas pressurizes the crankcase. The breather tube let the blow-by gas escape without pressurize the crank case. For car, it goes back to the air intake via the PCV valve.

In you case, there is oil in the breather tube. Which means the oil got splashed around too much in the crankcase or excessive blow-by gas during compression. There are 3 possible causes:

(1) It is possible the dip stick is not correct (or original) and you over filled the crank case. In that case, oil got splashed around and created foam. That got up to the breather tube. May be the oil is too light. Diesel engine usually use SD at 15W40.

(2) Too much blow-by gas due to worn ring (you need a compression test)

(3) Too much blow-by gas due to worn valve sleeve (May have to open the valve cover to check)

good luck
 
Jan 20, 2009
15
Endeavour 32 Fredericton, NB
Blowby

Hi Roger,
Here is an optimistic way to look at it that might be easy to test:
Oil has been forced out your rear main seal by high crankcase pressure but maybe the seal itself is not damaged. On my engine, and perhaps on yours originally, crankcase ventilation consists of a hose from the valve cover to the air cleaner causing no pressurization.

Is it possible that the pressurization kept increasing as the oil separator material became more saturated, with higher pressure causing more oil movement, faster oil separator material saturation and increasingly higher pressure until the oil seal popped?

I suggest you clean up the mess, top up the oil, disconnect the hose from the oil separator and direct it into a bottle, and try cautiously to run the engine. This will test whether the rear oil seal is still in place and sealing (maybe you'll be lucky) and give you a sense of the quantity and pressure of the blowby.

I'm guessing you put the separator in place due to concern about engine runaway from burning oil rich blowby vapors. I'm wondering whether you can solve the immediate problem by just disconnecting the oil separator. It would be interesting to get some experts opinions concerning the possibility of engine runaway if you go back burning your blowby vapors.

Paul from New Brunswick
 
Nov 22, 2008
3,563
Endeavour 32 Portland, Maine
Liquid oil slowly draining out of those teeny 5 micron pores could explain the difference
Now I know how the cops feel. Even though I found the guy leaning over the body with a smoking gun, he has an ironclad alibi. Always look at the obvious first.

When I did the quick and dirty test last night (after situation appropriate consumption of imported beverages) I had to pull on the breather tube to get my mouth on it. That kinked the hose at the back of the separator. This morning, with the engine compartment opened up, there was no tension on the hose. I just spliced in another piece of hose and was able to recreate last night's back pressure by pulling the hose to the position I had it in when I tried to blow through it.

I now have no evidence in hand to indicate that pressure restriction in the PCV system has any relevance to this situation.
 
Nov 22, 2008
3,563
Endeavour 32 Portland, Maine
I am convinced that your dipstick tube is the culprit ...
You wouldn't be if you had just looked at it and run a paper towel all over the area like I just did. It's about the cleanest part of the engine.
 
Nov 22, 2008
3,563
Endeavour 32 Portland, Maine
(1) It is possible the dip stick is not correct (or original) and you over filled the crank case. In that case, oil got splashed around and created foam. That got up to the breather tube. May be the oil is too light. Diesel engine usually use SD at 15W40.
These engines were installed in these boats several degrees above Yanmar's maximum shaft angle limit but it never seems to have caused a problem. At the top of the dip stick, I have a quart or two less than the rated capacity but this has never seemed to have caused a problem either. It makes overfilling much less likely. No question that it is the original dipstick based on photos and its very engine specific design with an "O" ring.

(2) Too much blow-by gas due to worn ring (you need a compression test)

(3) Too much blow-by gas due to worn valve sleeve (May have to open the valve cover to check)
The way this engine runs and starts, that's hard to believe. First start in the spring after winter layup and it lights off like it was in the middle of a summer daysail and all warmed up.
These are certainly things that will be checked next week though as part of assessing how much to put into rebuilding this engine.
 
May 24, 2004
6,045
CC 30 South Florida
Roger these are tough little engines, if you shut it down as quick as the oil pressure alarm went off the engine may be ok. I'm not saying that oil/air separator was not a good idea at the time it was installed but at this time it could be doing more harm that good. Every engine leaks some cylinder compression into the crankcase and well worn engines leak more. These presure that builds up inside the engine if not allowed relief will start oil leaks through gaskets and seals which under normal pressure would not leak. If the engine was running when you shut it down chances are it is OK. I would disconnect the oil/air separator and let the engine vent free. Fill it up with oil and start it. If it starts and runs then there is not much damage. With the engine venting free there should not be excessive pressure building into the crankcase and the oil may flow freely through the engine and stop leaking out any selas or gaskets. I have had some experience elongating the life of well worn engines. One way of reducing compression blowby is by increasing commpression and that can be done with the use of a thick oil. Generally I would fill with 20W-40 and a can of STP oil additive which pours like molasses. (substitute the amount of STP additive added for the corresponding amount of oil). This can make for a little hard starting in cold weather but once the engine warms up it will run fine. You will still have some oill condensate in the breather hose but it should be drops and not amounts as shown in the separator. You can direct the hose to an open can to collect the drops and prevent a sticky mess. There is no harm in removing the valve cover and looking around and in insuring there are no blocked oil passages. Once you get the engine oil situation stabilized there should be no problem int it getting you home but be gentle with it and run it a 3/4 throtle max. Mechanics may recommend a rebuild and they may be right but if you can postpone it until you get home then you can make a decision about it depnding on how much use you project after that. Before allowing for the engine to be cracked open I would definitely test with a thicker oil and free breather.
 
Nov 6, 2006
8,508
Hunter 34 Mandeville Louisiana
Wow.. Broke my bubble! once I saw that the dipstick tube was below oil level, I figured that the completely full reading on dipstick and the partially blocked breather had blown the oil out the top of the tube.. Back to the drawing board.. No breather issue maybe but the full dipstick is now a mystery too.
 
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