Yanmar 2GM20 oil exploding from dipstick hole

[Elie]

If the engine is blowing oil while runing, It implies compression into the base of the engine, where normaly, there should not. The engine is a 2 cylinders, and it would not run on one cylinder so blowby most be coming from the engine head, most probably a head gasket or a burned exhaust valve not closing tight. I don't believe that it is normal. I also think that the cylinder's head need to be lifted to go to the soruce of the problem. A compression test would certainly sort out everything. Good luck

[Kerry1]

As others have said, try the easier explanations first. Over filled oil, check color also, if water has made it milky plus blowby- suspect blown head gasket. Blocked breather system. Worn valve guides can also leak compression into sump through the blow-by pipe which may not be as dire as worn/broken rings. Does the engine start easily from cold? I have an old diesel which requires ether added to air intake to start on cold mornings like I need coffee to start the day. After that it starts fine, although runs a bit smoky!

Good luck.

[sb1]

Thank you all very much for the wealth of advice. Quite right, no PCV valve. I will be sure to do the simpler tests first - seeing how much pressure/fumes come from the opened oil cap, soaking the cover in turps overnight, checking the oil level and exhaust hose. In fact I'll check everything on the offending engine compared to the identical well-behaved one.

Interesting (if a little alarming) that it might be the head gasket. I had put that thought back as I would have expected some water to be getting into the fuel and/or oil with results that would manifest themselves in some (other) obvious way.

Originally Posted by Dulcesuenos

We had this and thought it was a bigger issue turned out the dipstick was just a little too loose AND our exhaust hose was old and has actually delaying aged internally and was blocking exhaust creating excessive back pressure.

Thanks Dulcesuenos, I hope this is it!

Originally Posted by rognvald

SB,
It would be helpful to know how many hours are on your engine and what has been the maintenance schedule since you've owned it. When you remove the oil fill cap when running, is there blowby(smoke/oil) or is it only from the dipstick? Is there any restriction in your hot exhaust(mixing elbow)? Is your oil filled to the proper level? These answers would be helpful to further diagnose your problem. I have seen hundreds of engines with blowby and have never seen anything other than smoke emanate from the dipstick or oil fill cap when the piston rings/compression was severely compromised.

Thanks rognvald. 2500 hours. Maintenance schedule sketchy and regarded with tongue-in-cheek. No smoke from oil fill aperture. None from dipstick either when no pressure, but probably due to its being below the oil level anyway as people have stated. I'll reduce the oil down towards the lower marker to see if the problem repeats.

Originally Posted by Elie

If the engine is blowing oil while runing, It implies compression into the base of the engine, where normaly, there should not. The engine is a 2 cylinders, and it would not run on one cylinder so blowby most be coming from the engine head, most probably a head gasket or a burned exhaust valve not closing tight. I don't believe that it is normal. I also think that the cylinder's head need to be lifted to go to the soruce of the problem. A compression test would certainly sort out everything. Good luck

Thanks Elie, your cruel logic makes absolute sense to me. Excuse my ignorance, but does a pressure test necessitate removing the head? Is a pressure test something that can be done by a careful novice with 10 thumbs but good intentions?

Originally Posted by Kerry1

As others have said, try the easier explanations first. Over filled oil, check color also, if water has made it milky plus blowby- suspect blown head gasket. Blocked breather system. Worn valve guides can also leak compression into sump through the blow-by pipe which may not be as dire as worn/broken rings. Does the engine start easily from cold? I have an old diesel which requires ether added to air intake to start on cold mornings like I need coffee to start the day. After that it starts fine, although runs a bit smoky!
Good luck.

Thanks Kerry - that sums up what I need to check. We don't get cold mornings here (well, it might get down to a chilly 16 Celsius at 6 am in the bleak mid-winter). We're spending the weekend on the boat so I'll keep you all posted.

Cheers!

Damo (sb1)

[SeaSon]

Originally Posted by a64pilot

There is no PCV valve on a Diesel, or I have never seen one anyway.
However there is almost always a form of air oil separator in the valve cover that of course keeps oil from being blown out, often it's just a mess of steel wool or similar, and it can become dirty and block airflow.
I'd take the valve cover off and soak it in a bath of mineral spirits and specifically look for sludge on the part where the blowby hose connects.
Of course too much oil will certainly cause this, you sure its not overfilled, and it has the correct dip stick?

My Ford Lehman have them. Or something extremely similar.

[Elie]

Taking the compression requires only to remove one a the time the injectors and insert in its place a fitting and a gage. then you crank the engine That in itself will tell volumes about the condition of your engine. If there is black oily stuff on the injector tip that is an malfunction indication. You will find out fast if a valve leaks. By the way, a burned gasket will eventualy reach a water passage, and then, you will find that your the oil has turned into an emulsion. And again, it is a good thing to have the head checked, all carbon removed, valves and seats polished and the valve seals renew etc... All this done at a good specialised shop, and not expensive. Kind of a new life for the beast! You will like it!.

[sb1]

Ha! I'm sure I will like it! But it presumably involves lifting the engine out of the boat (?) so perhaps I won't like the price so much.

I'm not complaining - it's all for a good cause. Thanks again for your help.

[Barney21]

Originally Posted by inchcailloch

We had this happen some 12 years ago, fortunately it was no more than the rubber on the dipstick having (disinterested)!. Hopefully, it is no more than this for yourself

Thanks for the smile.
I would suggest you have either a hole in a piston, alternately, top of the piston is stuck in the top of the bore.
Can you do a compression test?
Take the rocker cover off as suggested, that will prove the amount of blowby.

[sailah]

Originally Posted by sb1

Ha! I'm sure I will like it! But it presumably involves lifting the engine out of the boat (?) so perhaps I won't like the price so much.

I'm not complaining - it's all for a good cause. Thanks again for your help.

A compression test is done with the engine in the boat. You can remove either an injector or glow plug. Usually you need an adapter for the thread. So for example in my boat my glow plugs are M10 so you buy an M10 adapter along with the diesel compression tester. Probably $100 total.

Make sure fuel kill plunger is out like you were stopping the engine because you don't want it to run.

Thread the compression tester in and crank engine for a few seconds.

Max compression will be recorded on gauge. You continue to do this for all the cylinders and compare the readings between. More important than the ultimate reading is the difference between the 2 cylinders. That's a published spec. Deviations of more than 10% are suspect and indicate a problem.

If you find poor compression in a cylinder there are further diagnostics you can perform like putting a small amount of oil in the cylinder and rechecking it. If the pressure remains low, most likely cause is in the head. If compression raises markedly then the culprit is most likely the rings as the oil is temporarily acting like a ring and sealing off during when you were cranking.

None of it is complicated, just steps you need to follow and a few tools.

I would exhaust the comprehensive list that others have posted of free/easy things to check first.

[Elie]

Originally Posted by sb1

Ha! I'm sure I will like it! But it presumably involves lifting the engine out of the boat (?) so perhaps I won't like the price so much.

I'm not complaining - it's all for a good cause. Thanks again for your help.

In general, there is no need to take the engine out, unless there is not space at all to unbolt the engine head. And send it to the shop...

[taftke01]

This experience was not a diesel, but a Ford gas engine. After changing the oil and filter, oil started shooting up the dip stick, and running out. After trying many things, it was fixed by re-changing the filter. In conclusion, the new filter was defective and plugged, causing high back pressure to the oil circulation pump, which sprayed all over the under side of the engine in the oil pan. It found it's way up and out the dip stick tube. Hope your problem is the same, and fixed as easy.
Ken

[Dulcesuenos]

Originally Posted by Dulcesuenos

We had this and thought it was a bigger issue turned out the dipstick was just a little too loose AND our exhaust hose was old and has actually delaying aged internally and was blocking exhaust creating excessive back pressure.

Meant the exhaust hose delaminated internally creating back pressure and (fake blowby) God's autocorrect sucks.
And yes it was a 2gm20f

[sb1]

Originally Posted by taftke01

This experience was not a diesel, but a Ford gas engine. After changing the oil and filter, oil started shooting up the dip stick, and running out. After trying many things, it was fixed by re-changing the filter. In conclusion, the new filter was defective and plugged, causing high back pressure to the oil circulation pump, which sprayed all over the under side of the engine in the oil pan. It found it's way up and out the dip stick tube. Hope your problem is the same, and fixed as easy.
Ken

Thanks for that - good idea - sounds like something I can try without breaking anything. Just to give everyone a chance to experience some Schadenfreude, I started going through the list. The blow-by coming from the opened oil cap (a palm-of-hand precision test) was actually less with the offending engine than with the "good" engine. The oil was a little high - right at the maximum mark (and perhaps a tad beyond), so I pumped that out and refilled with the correct amount. Perhaps I should have left it there for a while to see if the problem repeated. Instead, I removed the mixing elbow, in the process breaking the head off one of the nuts. So I used a 2 mm drill bit to make a hole with which to use an "easy-out" to get the bolt shaft from the engine casing. Of, course, the drill bit snapped in its own hole. I then had a cold beer and watched the other boats coming and going (enviously). I do love it out there. I'll get back to the bolt when I can, and the rest of the list.

Cheers

Damo (sb1)

[a64pilot]

If there is any of the bolt sticking out you can sometimes get a vise grip on it, heat and PB Blaster and let it soak help.
I have also used a Dremel to cut a screwdriver slot in a broken off flush bolt too. Use an impact screwdriver, the kind you hit with a hammer, that knocks it hard into the slot so it doesn't strip and the percussion seems to help loosen the stuck stud.
I do not use easy outs anymore since discovering many years ago that when you break one of them off, you cannot drill it out, an easy out is as hard or harder than a drill bit.
Worst case, remove exhaust manifold and take to a machine shop.

[sfnz]

Had a bit of hilarity with exactly this happening to a 2QM20, engine on a trolley and test running before putting it back in, decide yep give it a clean, plugged up holes, taped dipstick etc, breather pipe from around injection pump area to air intake was missing/ not put on just yet so blocked holes at both end and washed and scrubbed and scrubbed and washed etc finishing with a quick water blast to really get it pristine and it WAS !!!, mate popped in and beer was had etc etc and naturally, as happens, decided to give at a quick run (showing off etc....alcohol was involved and yes I was trying this at home) unplugged all the holes hooked up fuel and battery and zoom away it went.....about a minute and a half later a small squirt of oil turned into a geyser out of the dipstick hole (dipstick shot about2' up and roughly4' across ) had unplugged all holes etc with the exception of that crankcase breather and almost knew straight away what caused it......mop up and next day another wash .........
another "IDIOT RASH" in lifes nautical journey

[RaymondR]

My 3GM30 had a vent line from the tappet cover back to the inlet manifold. If this was blocked it would result in a pressure build up in the crank case which might then expel oil out the dipstick hole. Pull the hose off and run a piece of wire through the hose and nipples on the tappet cover and manifold to ensure they are clear.