2GM20 Blows Out Oil

[Wotname]

You have the assumption that the dipstick problem and the oil pressure sender problem are related.

But are they really????

Regarding the dipstick, it is held in by friction and to a lesser extend, it's weight. Perhaps there is no longer enough friction in the "rubber" seal. You have an identical engine in the other hull so swap the dipsticks and see if the problem follows the dipstick or stays with the engine.

I don't have a good idea for oil pressure sender - yet! Are you talking about the low oil pressure switch (as fitted by Yanmar) or an oil pressure sensor for an aftermarket oil pressure gauge?

EDIT: I see Compass790 just asked the same question re the sender so it must be an important question !!!

[Compass790]

Another idea is if you think the rings are sticking is to remove injectors & spray or inject carb cleaner or some kind of decarb stuff down the bores & let sit overnite.
Might have to change oil if you use something aggressive

If you think the problem is related to engine sitting for long periods you could try removing the injectors before you leave it for a long period & squirting a bit of oil in the cylinders. Re -install injectors loosely, then spin it up with injectors removed to blow any oil out before starting next time tho I'd expect the oil to drain to sump if left for months.

I have no idea what size opening on a 2gm20 for the oil return from the rocker arms to the sump is via the pushrod galleries are but doubt it could be blocked as only filtered oil gets up there ordinarily unless the oil was contaminated with something that could precipitate out like seawater.

Another question is, does the blowing out of the dipstick only happen at high revs?

[Wotname]

Originally Posted by Compass790

Another idea is if you think the rings are sticking is to remove injectors & spray or inject carb cleaner or some kind of decarb stuff down the bores & let sit overnite.
Might have to change oil if you use something aggressive

If you think the problem is related to engine sitting for long periods you could try removing the injectors before you leave it for a long period & squirting a bit of oil in the cylinders. Re -install injectors loosely, then spin it up with injectors removed to blow any oil out before starting next time tho I'd expect the oil to drain to sump if left for months..............

I am lazier than Compass790 and if I wanted to induct some cleaning fluid into the cylinders I would simply remove the air filter and spray the stuff into the intake manifold while turning the engine over with the decompression lever operated, the engine stop lever in the stop position and the raw water seacock closed.

To remove, spin the engine over in the same manner.

[Wotname]

Originally Posted by Compass790

...........
I have no idea what size opening on a 2gm20 for the oil return from the rocker arms to the sump is via the pushrod galleries are but doubt it could be blocked as only filtered oil gets up there ordinarily unless the oil was contaminated with something that could precipitate out like seawater.

......

They are pretty big (huge even) but I don't remember the actual dimensions. I agree it would be highly unlikely and if they did clog, one would have other serious problems, not just a dipstick popping out occasionally.

[Compass790]

Originally Posted by Wotname

I am lazier than Compass790 and if I wanted to induct some cleaning fluid into the cylinders I would simply remove the air filter and spray the stuff into the intake manifold while turning the engine over with the decompression lever operated, the engine stop lever in the stop position and the raw water seacock closed.

To remove, spin the engine over in the same manner.

Dunno how much it would suck in tho cobber as decompressing the engine you are taking away most of the vaccuum. Would it get to far cylinder? I haven't tried it I'm asking. Must admit I used the non-decompressed method to get oil into the cylinder to raise compression for a start before I rebuilt engine. Bent pushrod once tho injecting too much

Good point that oil pressure alarm may well be unrelated to dipstick launches

[skipperpete]

Originally Posted by Sonosailor

Hi Guys: I’m at my witts’ end.



1996 2GM20F: Please give me all the reasons this particular engine could throw out the dipstick and then spray the engine room with all the oil. I’ll respond with my knowledge and efforts.



Understand that less than 50 hours of run time ago, I ran the engine with mineral spirits instead of oil, to clean out carbon deposits, after it pushed the stick out a couple of times, and was being suspected of clogging the oil pressure sender. Each time this happens, I check the crankcase blow-by apparatus which, as you know, is terribly simple on the 2GM20.

The most logical reason for the crankcase pressure would be a blown head gasket to the pushrod galleries but it could also be massive piston ring blow by as a result of the lube oil system flush. You might have scuffed the rings and liners with whatever hydrocarbon you used to carry out that procedure. Getting the head off a 2GM is a pretty easy task and will provide you with a firm diagnosis and the opportunity to do a top overhaul ......look carefully for cracks around the skinny bit between the valves and precom outlet.
Did you see any loss of coolant or increase of toptank pressure, if the head gasket is leaking it might also be apparent there too.

[Wotname]

Originally Posted by Compass790

Dunno how much it would suck in tho cobber as decompressing the engine you are taking away most of the vaccuum. Would it get to far cylinder? I haven't tried it I'm asking. ........

Well with both the inlet and exhaust valve open, the suction on the intake stroke should be equal between both the exhaust and inlet valves so yes, some stuff should be inducted via the inlet manifold. Of course if you have a bunged up exhaust system, you will get more in via the inlet side

There is only one intake port on the inlet manifold and it is equidistant between the two inlet valves.

But as you know, I ain't a diesel mechanic .

[Compass790]

Originally Posted by Wotname

Well with both the inlet and exhaust valve open, the suction on the intake stroke should be equal between both the exhaust and inlet valves so yes, some stuff should be inducted via the inlet manifold. Of course if you have a bunged up exhaust system, you will get more in via the inlet side

There is only one intake port on the inlet manifold and it is equidistant between the two inlet valves.

But as you know, I ain't a diesel mechanic .

Hey I'm thinking that's smart not lazy. I bow to your greater 2GM20 knowledge.
Thanks for the explanation cobber.
I imagined a single intake at one end. AGAIN assuming got me into trouble!
As you know I aint a diesel mechanic either.

[Compass790]

Originally Posted by skipperpete

The most logical reason for the crankcase pressure would be a blown head gasket to the pushrod galleries but it could also be massive piston ring blow by as a result of the lube oil system flush. You might have scuffed the rings and liners with whatever hydrocarbon you used to carry out that procedure. Getting the head off a 2GM is a pretty easy task and will provide you with a firm diagnosis and the opportunity to do a top overhaul ......look carefully for cracks around the skinny bit between the valves and precom outlet.
Did you see any loss of coolant or increase of toptank pressure, if the head gasket is leaking it might also be apparent there too.

Yea skipperpete,
Thought this too ( blown gasket) but scroll down to btm of screen & see OP had the same thread in 2012 & had no trouble assumedly btwn then & now. Look in similar threads section for his earlier postings.
Would have thought blown gasket would have deteriorated more in that length of time but it's just a guess
I'm leaning towards ring sticking from leaving it lying for 7mths at a time. but yes he might have to pull head off in the end.
I too wondered what would happen using turps as engine oil. I'm a risk-taker but it sounded a bridge too far to me. Have heard of using diesel many times as flushing oil but I'm not game.
Hope OP answers questions.
Got another one for him. How many hours on the engines?

[jimbunyard]

Originally Posted by Sonosailor

Thanks guys, but nothing new suggested yet.

Crankcase blowby: Those of you who know the engine know that it is tough to block and easy to check. No foam, no screen no filter; just a little baffled box on top of the valve cover that runs to a 3/8" short tube to a 3/16 or so opening downstream of the air filter in the air intake. No sign of a problem whenever this happens. The air filter is not saturated with oil, and there never seems to be a significant issue in the hose or the intake, wrt oil residue, well, maybe a drop in the hose, to be fair.

Occurrence: This doesn't happen every time I start the engine. I could go weeks without an issue, then bam: I uncover the engine to find the compartment in a *&^%ing mess. I could run it for days with the cap off, and possibly not have a problem.

Engine performance: The engine works great, starts easily, makes no funny noises; and delivers propulsion without complaint just like its sister in the other hull. It does make a little more smoke when quickly accelerating and when backing on anchor at 2000rpm (after the chain is already tight), than its sister, but not much.

Engine maintenance: Boat is used only 5 months per year in the Caribbean. Each layup involves a complete oil and filter change. I am a sailor, and long engine use only occurs when I am buddy-boating. It did this fall, and that is the only reason we have 40+ hours since the oil change.

Why the mineral spirits: Six years ago, this was happening a lot. A Yanmar guy in Guadeloupe said he was sure I had a faulty fuel pump filling the crankcase with diesel and that was doing it. He sold me a "rebuilt" pump, and I put it on. Indeed, it was not rebuilt, but did have the busted diaphragm. The fuel did go into the crankcase, did come out the blowby, and I had a runaway engine with diesel in the crankcase. I got the engine stopped, sorted it all out, stopped trusting dealers and counter-people, and put the old pump back. When I told it all to a seasoned Yanmar mechanic, he said I might find that I had fixed the oil problem by running it wildly fast with diesel as the solvent in the crankcase. He was correct, and I had no problem until last spring. The suggestion was stuck rings, which sometimes caused the problem, and the diesel unstuck them. I was told to increase rpm to decrease carbon in both the oil and the mixing elbow. I have, and certainly the mixing elbows are doing better.

Last spring, I not only had the oil spurting out twice, but had oil pressure senders malfunctioning regularly. Another qualified diesel mechanic told me to try the mineral spirits, but with the crankcase blowby sending to a pail. I did not run the engine hard, but just enough to get the equipment well rinsed. It worked for 40 hours: no oil pressure sender problem, oil pressure in the correct range checked with a guage, and no kicking out of the oil stick.

Now here I am again. Did I miss anyone? As always, I appreciate all comments. No matter what you write it stimulates the brains of the rest of us.

Also, I have to ask: What is the way that the crankcase venting gets up to the valve cover, to exit the crankcase blowby baffle and hose? Is that something that could become blocked and cause excess pressure in the crankcase that cannot get to the valve cover area?

Something seems strange here.

There is no other mechanism for oil to be 'blown' out the dipstick tube than excessive (unrelieved) crankcase pressure; if the dipstick tube was raised so that oil couldn't be sucked out for an oil change, it wouldn't be pushed out by cc pressure.

That the engine runs well would preclude any problems with rings or head gaskets or valve sealing (induction, exhaust or guide); 'mechanics' recommending 'mineral spirit washes' for, apparently, intermittently sticking rings (who ever heard of that? or of them mysteriously [sometimes] 'fixing' themselves?). Next time you want to 'unstick' your engine's rings, save the wear on them and the cylinder bores by using something with some lubricity, like diesel.

If you change your oil via the dipstick tube, probably the reason your oil was so clean after the mineral spirit wash was that there was likely a substantial amount of mineral spirits left when you refilled the engine. The 'oil system flushes' one can buy from the parts stores, which are primarily the same thing as mineral spirits, generally recommend diluting the engine oil, not replacing the oil outright...

As for a hypothesis as to what is happening to you, from the 2 dimensional parts breakdowns available online, here's one.

The two chamber breather apparatus built into the valve cover ('bonnet' in the manual) has, in the smaller, exhaust side chamber, a small drain hole that, periodically and sporadically, becomes blocked, allowing oil to fill that chamber and cut off the normal flow of pressure to the breathing system. The difference between the pressure to push the oil out the breather versus out the dipstick tube is so small that sometimes the breather works as engineered, and sometimes the engine works as an 'auto oil removal device'.

Without being there it's all imagination, if I were there though, my first step would be to remove the valve cover, dis-assemble the breather completely, verify exactly how it functions and physically check that all passages are open and clean.

I can think of no way that crankcase pressure could affect oil pressure switches or senders; they operate in a closed sustem, if the oil pressure were low enough that crankcase pressure overrode them, the engine would seize before it built enough crankcase pressure to override the switch/sender.

[skipperpete]

Originally Posted by Compass790

Yea skipperpete,

Thought this too ( blown gasket) but scroll down to btm of screen & see OP had the same thread in 2012 & had no trouble assumedly btwn then & now. Look in similar threads section for his earlier postings.

Would have thought blown gasket would have deteriorated more in that length of time but it's just a guess

I'm leaning towards ring sticking from leaving it lying for 7mths at a time. but yes he might have to pull head off in the end.

I too wondered what would happen using turps as engine oil. I'm a risk-taker but it sounded a bridge too far to me. Have heard of using diesel many times as flushing oil but I'm not game.

Hope OP answers questions.

Got another one for him. How many hours on the engines?

I’m no fan of the lube oil flush with anything but engine oil. If the engine is very dirty internally and it’s flushed out by a solvent of some type it can only go to the bottom of the oil pan as sludge ... which might be ok if it had a removable sump plug to let all the goo ooze out but the GM series engines don’t have a drain plug and the oil pump suction strainer is the lowest point in the oil pan, potentially immersed in sludge.

[Sonosailor]

Originally Posted by Compass790

Ok sorry I added nothing but it sounds like you have a rare problem to state the obvious.
Can you elaborate more on what happens with the oil pressure senders?
Are these just alarms or to oil pressure gauge?
I assumed your crankcase breather came from the crankcase rather than rocker cover as it does on our Yammer. Shuda checked first.
My GUESS is the crankcase pressure comes up thru the pushrod galleries but will check later on 2gm20 as I've messed up on breather pressure path.

The oil pressure sender would start alarming, meaning that the engine startup pressure would not cause the contacts in the sender to separate. A mechanic suggested this might be because of the carbon gunk, and possibly the same gunk was sticking rings and or otherwise causing the oil to get pumped out the stick hole. A temporary replacement of the sender with fittings and a gauge allowed us to see that the engine performs within the proper parameters with respect to oil pressure. A new sender was installed after the clean out, and has been working well.

Thanks for your time on this.

[Sonosailor]

Skipper Pete said: “
I’m no fan of the lube oil flush with anything but engine oil. If the engine is very dirty internally and it’s flushed out by a solvent of some type it can only go to the bottom of the oil pan as sludge ... which might be ok if it had a removable sump plug to let all the goo ooze out but the GM series engines don’t have a drain plug and the oil pump suction strainer is the lowest point in the oil pan, potentially immersed in sludge.”

I see your point, but I sucked the mineral spirits out, cleansed the interior with an oil change and running, then changed the oil again. It did solve the problem, and for a long while I had see through oil on the dipstick - new to me for the years I have been the owner, so I have to assume it did some good. Again, the first time was an accident, and the second time under the guidance of a qualified person. Yes, the breather/crankcase blowby was disconnected from the air intake for the treatment.

[Sonosailor]

Jim Bunyard:
“Something seems strange here”: I’m with ya buddy!
Mineral spirits may have stayed behind: I followed the spirits flush with an oil flush of similar duration, and both flushes were sucked out as quickly as I could do it. Then I changed the oil.
Commercially available oil system flushes...: I have in my hand “H% Heavy Duty Motor Flush”, that promises to do the job WITH THE OIL in 5 minutes. That is what I may try next time. As the 2GM20 only holds ~2 litres, I will have to suck some out to get the 0.9 L of flush in.
Rechecking the breather: As your diagram and your experience tells you, four #10 bolts and it is an open book. The hole is clear.

Thanks for your attention, and please don’t stop.

[skipperpete]

Hi OP
Thanks for responding to my concerns re lube oil flushing. As a more palatable option to removing the head, why not do a compression test or even better, a cylinder leakage test. This way you only have to take out the injectors and you will definitely know more about the source of the oil spray. I couldn’t remember whether the 2GM20 dipstick had a tube to the bottom of the oil pan ( it doesn’t) but that made me think that the oil level might be too high from?. Fuel leaking into the sump? Coolant maybe ..... but it still wouldn’t explain why the dipstick is getting blown out. That must be crankcase pressure.