Yanmar 2GM - water in oil - help!

[HappyMdRSailor]

Originally Posted by sailorchic34

Ah rats, My secret is out

Well from about age 6 onward I watched my dad when he fixed anything on the car. I was a pretty good tool getterer too. Besides having a general engineering background, I have a curiosity about how everything work, So I tend to read just a whole lot. Plus I have the Yanmar GM series service manual . I also learned hands on engine repair with a 71 VW bus and a Triumph Spitfire. Weird Girl I know.

The water engress almost has to be a bad head gasket. The aftermaket fresh water cooling system, if its yanmar is basically the same components as the regular 2GM20F.

I knew it !

Anyhoo.... cool background and story... Wish kids were like that today regardless of gender... All I ever hear is Mario this... Wii that.... The merits of DS v. 3DS blah bla blaaaahhhhh....

Had TR's myself... 3A, 4A, TR8. Showed the 3 and the 8, many a Triumphfest and the like....

Let's get this guys Yanny uh-fix-ed!

[dr_c]

I love it. With any luck, I’ll get my daughter hooked on helping me fix our LBC (a ’79 MGB) and sailing. At 2, she’s probably too young to understand you should be a role model.

Here’s where we are with the diagnostics:
• Turns out the local Yanmar marina in Portland, Maine has some machine shop capabilities. I’ve dropped the head and head gasket for inspection, and they’re going to figure out what they recommend (probably magnafluxing and a valve job). They think I probably started the motor while hydrolocked. Based on what I now know, I would agree.
• The block passed my poor-man’s crack test (fill the block with coolant and watch for a drop in level).
• I measured the piston height (~0.5mm above deck) and stroke (~72mm) for both pistons with a cheap caliper – they seem the same within my ability to tell; *knocks on wood* Perhaps I haven’t damaged a connecting rod. . . of course, if these things need to be measured in thousandths, I wouldn’t be able to tell.

The narrative so far: the pressure from starting under hydrolock blew the head gasket, allowing coolant into the oil. The mechanic seemed to think that it wouldn’t take much coolant in the oil to cause a low pressure warning . . . so we’ll see.

I'll post updates as I learn more and start to get this back together. . .

Cheers,

-Tony

[HappyMdRSailor]

Tony...

Sounds like you are on the path to righteousness.... Mostly with your daughter!

Anyway.... Sounds like a perfectly sound process is in place...

The mechanic seemed to think that it wouldn’t take much coolant in the oil to cause a low pressure warning . . . so we’ll see.

I agree...

You have an external raw water pump, so that's out.... Any oil cooler???

Keep us advised of the progress!

[gjordan]

dr-c , The shop that is going to do the work on the head should have the ability to pressure test the head in addition to magnaflux. There can be internal passages that are cracked, but everything that is visible will show up as being good. I believe they make a jig(flat plate) with holes to allow air pressure into the oil passages, head is bolted and gasketed to the jig, and then see if they hold pressure. Same done for water passages. I once had the job of finishing an overhaul of a 4 cylinder generator engine that had been disassembled because of water in the oil. I found a small crack in a cylinder liner and thought that I had found the problem. Changed the liner(miserable job) and proceeded to reassemble the engine. The head had already been sent to a machine shop for overhaul. I installed the freshly overhauled head and all of the other little bits and put oil in ,getting ready for a test run. I then put coolant in and when full, I could hear a little trickle of water running into something. I removed the oil filler cap and could clearly hear coolant running into the oil. The nice freshly overhauled head had an internal crack that could not be visibly detected. If the mains or one of the other generators had been running, I would not have heard the trickle and would have started it up with water in the oil again. Just another of the school of hard knocks lessons. ______Grant.

[Nor'Sea 27]

Please satisfy yourself as follows. A hydro-lock event means water flowed into the cylinder via an open exhaust valve. There are two possibilities:
1) you ran the starter motor a considerable period of time, sea water pump "overflowed" sea water into the exhaust chamber, through the exhaust valves, and into the cumbustion chamber. You would notice because the starter motor will stop turning almost instantly.
2) the exhaust elbow water/exhaust gas separation has disintegrated and sea water supplied by the sea water cooling pump passes to the exhaust manifold instead of into the exhaust tube and overboard. You will not notice this event because the water essentially drains into the cumbustion chambers. You would probably see a fair bit of corrosion (rust) inside the exhaust port
If the liquid in the cumbustion chamber came from a fractured head then testing the head will tell you. The liquid in the oil would be coolant - not seawater.
It is a little bit difficult (for me) to understand how a hydrolock (or coolant leak) to the combustion chamber could result in a head gasket failure. At the risk of repeating myself take apart, clean, and make certain the mixing elbow is completely intact and funtions as it was designed to.
When in doubt - take the mixing elbow to the guy who is doing your head, or call Compass Marine - Maine Sail who is nearby.

Charles

[dr_c]

Hi Charles,

I completely hear you - the mixing elbow is going to the recycle bin and I'm replacing it. It's easy to get at while the head's off and is of uncertain age. Cheap insurance.

Regarding how hydrolock might have occurred, there was a big storm that blew through (I think it was in September) the Sunday before this happened - in the anchorage, we had boats overturned on their moorings and plenty of shredded canvas. I didn't think much of it at the time, but when I went to start the engine, it was: on, start button, click and. . .nothing. I didn't know what hydrolock was, so I thought maybe my bilge pump had weakened by battery. Threw the battery switch to both, hit the button and. . . nothing. As I recall, I hit it a few more times, finally got a stubborn movement and then everything came to life - until the low pressure warning went off. My guess, now, is that the rough seas tossed the water in the water muffler up into the mixing elbow and into whichever cylinder had the exhaust valve open.

Regarding how could hydrolock blow the head gasket, particularly in a way that would allow coolant to mix into the oil. . . well, I don't exactly know. The mechanic down at PYS says that head gasket damage is the most common thing associated with hydrolock on the 1GM/2GM/3GM. What keeps me scratching my head is: How could hydrolock in a cylinder would cause a leak that would allow coolant into the oil, without particularly damaging the compression in the cylinder (it still started, twice)? I'm guessing either the cylinders are leaking and I just didn't notice, or the leak was transient and across the face of the gasket, enough to ruin the seal wherever it wasn't metal-reinforced. As we peel the onion, we'll see whatelse is in here.

Wish me luck!

-T

[Nor'Sea 27]

Terrifying story and glad I missed the show.

Agreed that water in the combustion chamber can lead to gasket fail - no matter how it got there and provided it was present there for a spell. But even with these additional facts - one would still be interested in opportunity to examine mixing elbow to assist the diagnoses. But - if it is in the landfill then no problem.

Since the event included water in the oil - the water had to reach the crankcase via a head gasket fail or via bypassing the piston rings. Accordingly before you put the head back on examine the piston bores to rule out corrosion on the bore surfaces.

Obviously a report on the present condition of the head cooling chambers will be useful.

Charles.

[dr_c]

Regarding the piston bores, a picture is worth 1000 words - if you look at the cylinder bore, you'll see white spots, but what isn't so apparent is that it's actually a mirror-like surface reflecting the spots on the piston head. What are the spots on the piston head? Frost! It was snowing outside they day I took this picture. Need to get this rig back together. . .

I'll post some mixing elbow photos once that's removed.

Cheers,

Tony

[Cheechako]

How much ridge is at the top of those cylinders?

[perchance]

As long as you have the head off measure the depth from the block to the piston top at tdc on each cylinder to ensure the hydrolocking didn't bend a connecting rod.

[dr_c]

Perchance - I actually did. Both cylinders seem to have the same piston height (~0.5mm above deck) and stroke (~72mm), within my ability to tell.

Cheechako - what do you mean, 'ridge'? In the area where the piston doesn't travel?

-T

[perchance]

Originally Posted by dr_c

Perchance - I actually did. Both cylinders seem to have the same piston height (~0.5mm above deck) and stroke (~72mm), within my ability to tell.

Cheechako - what do you mean, 'ridge'? In the area where the piston doesn't travel?

-T

He is referring to the ring of metal left behind as the bore wears away from the piston rings since they don't come all the way to the top of the cylinder.

[Cheechako]

Originally Posted by dr_c

Perchance - I actually did. Both cylinders seem to have the same piston height (~0.5mm above deck) and stroke (~72mm), within my ability to tell.

Cheechako - what do you mean, 'ridge'? In the area where the piston doesn't travel?

-T

Yes, the more of a "step" between the travel zone and the untraveled zone, the more worn your engine is. No shelf would be like new.
Also, better spray those cylinders with some WD40 or etc while it's sitting apart...

[Neo]

Very interested in the resolution to this problem. We have a 2GM that runs well, but there are indications that a small amount of oil is getting into the coolant.

My uneducated opinion:

Probably not seawater from a bad mixing elbow, which would have shut the engine down before large amounts of water could pass the piston and get into the oil (the engine stalled within minutes of changing oil and restarting engine).

However, if the head gasket is blown between a cooling port and an oil port (or the head is cracked), coolant could get into the oil quickly and drop the oil pressure. As the oil water mixture passes the rings and coats the cylinder walls, it could have stall the engine.

One problem with this scenario is the pressure differential between the oil and coolant would more likely cause oil to enter the coolant. However, if Sailorchic
is correct, then the oil pressure in the return would be low enough for the above scenario.

[dr_c]

Originally Posted by Cheechako

Yes, the more of a "step" between the travel zone and the untraveled zone, the more worn your engine is. No shelf would be like new.
Also, better spray those cylinders with some WD40 or etc while it's sitting apart...

Since it will be a couple of weeks until I get to putting everything back together (head's at the shop, parts haven't been ordered, we're getting more snow), I went up this evening to spray both cylinders with WD40, put one at TDC and shove a rag in the other one. The ridge was just carbon and dissolved in the WD40 - no ridge that I can feel. (knocks wood) Starting to think I'll feel pretty good about this little motor once it's back together. (keeps knocking wood)