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Old 29-08-2015, 11:50   #16
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Re: 3gm30f problems

Inspect the pistons closely while out. Especially the lower ring lands.
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Old 29-08-2015, 12:44   #17
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Re: 3gm30f problems

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Originally Posted by AsTheWindBlows View Post
Was that socket something you got from the yanmar dealer?
Yanmar does offer one for sale at $187(2013 price) that looks to be pressed steel.

I took a $25-$30 36mm socket to a welder and for 60 bucks he cut it in two and welded each piece toa piece of tube. Welding being a skill that I'm so not good at. If you can weld it's easy to make.

Very heavy duty and far cheaper then Yanmar price.
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Old 29-08-2015, 17:31   #18
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Re: 3gm30f problems

[QUOTE=jimbunyard;1902380]
the bearing is sacrificial; i.e. the brg disintegrates before the crank is 'toast'.

That is pretty much poppycock. All bearings are soft. Very soft, but that does not make them sacrifical to save the crank. The best of luck with your crankshaft condition but don't think the bearing gave it up to save your crank.
That ain't no WAG either.
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Old 29-08-2015, 20:31   #19
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Re: 3gm30f problems

[QUOTE=Guy;1902929]
Quote:
Originally Posted by jimbunyard View Post
the bearing is sacrificial; i.e. the brg disintegrates before the crank is 'toast'.

That is pretty much poppycock. All bearings are soft. Very soft, but that does not make them sacrifical to save the crank. The best of luck with your crankshaft condition but don't think the bearing gave it up to save your crank.
That ain't no WAG either.
Please, don't be coy, do tell why crank and rod bearings are soft, I love getting educated.

And by the way, an average crankshaft has a Brinell hardness of about 260-300, an average babbit brg maybe 20 Vickers and an aluminum brg maybe 40 Vickers. In this range, I believe the two scales are close enough to be interchangeable.
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Old 29-08-2015, 20:45   #20
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Re: 3gm30f problems

[QUOTE=jimbunyard;1903005]
Quote:
Originally Posted by Guy View Post

Please, don't be coy, do tell why crank and rod bearings are soft, I love getting educated.

And by the way, an average crankshaft has a Brinell hardness of about 260-300, an average babbit brg maybe 20 Vickers and an aluminum brg maybe 40 Vickers. In this range, I believe the two scales are close enough to be interchangeable.
Oh and then there is a nitrided surface which is really hard and lets don't lets forget chrome. That one is a biggy. You not only get a super hard surface but you can build up a damaged undersize surface with chrome. They all fail when the bearing goes. It's the oil dude.
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Old 30-08-2015, 07:11   #21
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Re: 3gm30f problems

Guy,


Suggest you Google 'wear metals' or 'crankshaft hardening processes' or even 'sacrificial'

From the first site of the first search under 'wear metals in oil analysis':


Lead (Pb)
A soft metal used for sacrificial wear surfaces such as journal bearings. Lead based babbitts are widely used .

Tin (Sn)

Tin is used as an alloying element with copper and lead for sacrificial bearing liners.


sac·ri·fi·cial
ˌsakrəˈfiSH(ə)l/
technical
designed to be used up or destroyed in fulfilling a purpose or function.




And from the real world side, I personally have several times peeled bearing metal off a crankshaft, polished the crank as smooth as possible with 120 grit emery cloth, put new (standard size no less) bearings back, and run the engine (albeit with slightly reduced oil pressure) as normal for years.

So it doesn't seem to be 'poppycock'. Nice chance, however (unfortunately) inaccurate it is, to use the word though...
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Old 30-08-2015, 09:02   #22
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Re: 3gm30f problems

Engines do not work with metal to metal contact, period. The coating on a bearing shell is so thin it would be gone in a nano second if it touched the journal. The sacrificial aspect of a bearing is for dirt, erosion etc. Even the acid from not changing your oil removes bearing material.
The OP had I think .060 slop on each end of the throw, so .120 wear on the bearing. That is way way beyond the probably.001 "sacrificial"tin coating on a bearing shell. Through the next layer and so on. So now he is down way past the copper that they electroplate the coatings onto and into the base of the shell.
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Old 30-08-2015, 10:01   #23
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Re: 3gm30f problems

Thank you for the thoughts everyone. As expected on here there are a few people who have done and lots of experts who have owned an engine at some point.

Sail forums make me smile. Every one who has changed oil becomes an expert. Offroad and performance forums don't get that way for some reason. Has to be frustrating for the few that know and run off the real sources.
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Old 30-08-2015, 10:43   #24
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Re: 3gm30f problems

.06" on each end would be........06" wear on the bearing, for a total cumulative movement of .12".

So what, if you have one, is your point? That sacrificial parts stop being sacrificial at some predetermined level? That you can't run an engine without oil? That dirt and acid cause engine wear?

The OP asked what people thought about his hopes to repair his engine successfully based on the information he provided. Several people gave reasoned replies, with ranges of expectation. You replied his engine was 'toast', which seems to mean nothing at all, since even with granma's best blackberry jam, a 3GM30F hardly seems appetizing...
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Old 31-08-2015, 00:17   #25
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Re: 3gm30f problems

I don't know how thick the bearing coating would be, but definitely thicker than .001". I have seen bearings with deep scores still in the bearing surface.

In the case of this engine, it appears the problem occurred in a short period of time, unlike the wear that would be expected from the constant pounding of running for many hours with increasingly worn bearings.

I doubt that the crank would be worn from this apparently short episode. But it could still be damaged. If the bearing did wear theough the soft lining, it may well have scored the journal, thus necessitating a grind.

So it's certainly worth checking out, as it's possible it survived OK.
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Old 31-08-2015, 20:20   #26
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Re: 3gm30f problems

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I don't know how thick the bearing coating would be, but definitely thicker than .001". I have seen bearings with deep scores still in the bearing surface.
rvived OK.
The thin sacrificial coating I'm talking about is on all new bearing shells. It's very thin. Race car engine builders wipe it off with a scotch brite pad because they don't need it or want it. Under that are different layers of different materials. It is a big heat sink also so choices are made for that issue too. The crankshaft is supposed to live on that first layer after the thin one. When it gets past that layer you get wear on the crank journals. If you get to it in time you can reuse the crank but you are only talking a few thou . Not that much. People who scrape off pieces of welded on bearing and call it good are just getting by. Aside from pistons and valves a crankshaft journal is just about the most stressed part in the engine. To mickey mouse it's repair is foolish, unless you don't have a choice of course.
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Old 01-09-2015, 03:49   #27
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Re: 3gm30f problems

Just how did a 30+ year old marine diesel design morph into a race car engine
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Old 01-09-2015, 04:17   #28
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Re: 3gm30f problems

Quote:
Originally Posted by Wanderlust View Post
I don't know how thick the bearing coating would be, but definitely thicker than .001". I have seen bearings with deep scores still in the bearing surface.

In the case of this engine, it appears the problem occurred in a short period of time, unlike the wear that would be expected from the constant pounding of running for many hours with increasingly worn bearings.

I doubt that the crank would be worn from this apparently short episode. But it could still be damaged. If the bearing did wear theough the soft lining, it may well have scored the journal, thus necessitating a grind.

So it's certainly worth checking out, as it's possible it survived OK.
Depends on what type bearing you're talking about, Bi-metal bearings have an aluminum/tin/silicon (and possibly copper) overlay thickness (before you get to the steel backing) of about .012". Tri-metal bearings have a first overlay of babbit metal of only .0005-.0008" thickness, followed by a very thin barrier coat (.00004-.00008") of nickel, and a final layer (before you get to the steel backing) of copper/lead/tin alloy .01-.015" thick.

Broadly speaking, the actual 'service' or 'sacrificial' feature of both bi and tri metal bearings is .01 -.015" thick, pretty thin, but still 10 times thicker than .001".

For more information than most people need or want, there is a good, basic explanation of bearing construction and destructive testing, including descriptions of some types of metal to metal contact in engines and applications, here;

http://kingbearings.com/files/Engine..._Materials.pdf

Everything else you said makes sense to me also.
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Old 05-09-2015, 13:17   #29
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Re: 3gm30f problems

A diesel has high bearing loadings because of the compression required to ignite the fuel. High compression means high heat in the combustion chamber to start the diesel burning when it is injected into the combustion chamber. If a diesel engine looses oil pressure there is no oil to carry away the heat caused by friction and the soft babbitt bearing material will heat and melt. This can happen quickly when an oil pump fails or engine oil is lost. So, if a diesel engine starts to run out of oil and there is no audible alarm indicating that oil pressure is going down, better figure on pulling the engine and doing a complete dissassembly including removal of the crankshaft. Get micrometer readings on the bearing journals (the part of the crankshaft that rides on the bearings) on the crankshaft. The journal has to be less than .0005 thousandths out of round and wear less than .001 if I remember correctly for an automotive size diesel. The thickness of a page from your computer printer is .006 so you can see the tolerances are very close. This is why changing oil and oil filter regularly is so important for engine life. A modern crankshaft in a diesel (Yanmar for instance) is hardened using electrical induction to heat and quench the crankshaft. There are other older methods that are more expensive, but make very hard journals. If a crankshaft journal is damaged, the crankshaft can be taken to a specialized shop, those usually only deals with crankshafts. The journals can be reground and undersized bearings used, or if too much journal material is worn away, there are methods for adding new steel to the journal area and then grinding the surface to standard size, or less if other journals require only grinding to standard undersize. Do not try and do a patch up job with a diesel. The parts are expensive, and engine failure at the wrong time is something you want to avoid.
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Old 06-09-2015, 09:55   #30
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Re: 3gm30f problems

Well, it all doesn't really matter. The fact is, soft or hard , a bad bearing will and does destroy crankshafts. I've seen many.
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