Yanmar 4JH4-TE Catastrophic failure

[knotbad]

Originally Posted by DougR

The con-rod bolt that is in one piece loosened and fell out of the rod, and the engine continued to run at the moderate 1400 RPM with low load, and the rod cap was held in place by the second bolt. When the vessel surfed down the wave the RPM raced and overloaded the remaining bolt and it fractured, allowing the piston and rod to remain up in the cylinder until the next revolution of the crank. When the crank came around next time it jammed the rod up against the block, spinning it 90 degrees, bending it and fracturing the piston.

No evidence of any other damage.....no seized piston, no damaged bearing shells, no scored journals.

The bolt that is not broken shows no evidence of rubbing or wear between it and the rod cap, it just loosened and fell out. But the broken bolt shows lots of shiny wear evidence against the inside of the rod cap holes.....evidence of flexing and rubbing as it continued to run.

Its difficult to see the grain structure of the bolt fracture surfaces, so we cant see evidence of a progressive fatigue failure (beach marks or two different grain structures) on the threaded end which is still in the con-rod. However it probably fatigued and then failed from an abrupt overload.

If I was a betting man, I would put my money on Doug R's comment. There is no other way the con-rod bolt (that is in one piece) could have escaped its proper position unless its threads were stripped. By the look of things, the con-rod was in its unusual position upon disassembly (ie: assuming the mechanic didn't undo the unbroken bolt and remove the cap)
The Turbo exhaust outlet is fairly typical corrosion, that is the results from exposure to salt air. This is fairly common on pleasure boats that sit in marinas for most of their lives, and especially those that don't have a flapper or water trap and exit just above the water line.

IMHO

Allan.

[Phil Lovering]

Hi Hunterdog,
A failed conrod is VERY unusual! I’ve spent a lot of my professional career analysing machine failures, and would be happy to help here.
If you could take close-up pics of the fracture surfaces and a few of the rod in general I could probably give some advice on ‘mode of failure’. Then you may have a claim on the manufacture.
Regards
Phil L

[Hunterdog]

Will do Phil. Thanks for offer!!!

[Hunterdog]

Originally Posted by Phil Lovering

Hi Hunterdog,
A failed conrod is VERY unusual! I’ve spent a lot of my professional career analysing machine failures, and would be happy to help here.
If you could take close-up pics of the fracture surfaces and a few of the rod in general I could probably give some advice on ‘mode of failure’. Then you may have a claim on the manufacture.
Regards
Phil L

Will do. At the moment, the rod is still stuck inside the engine. It’s wedged in there so hard, I may damage it more just removing it

[Hunterdog]

Originally Posted by knotbad

If I was a betting man, I would put my money on Doug R's comment. There is no other way the con-rod bolt (that is in one piece) could have escaped its proper position unless its threads were stripped. By the look of things, the con-rod was in its unusual position upon disassembly (ie: assuming the mechanic didn't undo the unbroken bolt and remove the cap)
The Turbo exhaust outlet is fairly typical corrosion, that is the results from exposure to salt air. This is fairly common on pleasure boats that sit in marinas for most of their lives, and especially those that don't have a flapper or water trap and exit just above the water line.

IMHO

Allan.

Here’s the bolt close up. Looks to me it went for a bashing ride. Mechanic said he found it in the pan.

[Michael Cobbe]

1200 hours


That's a long time marine engines are designed for 8,000 hours.

[Hunterdog]

Originally Posted by knotbad

If I was a betting man, I would put my money on Doug R's comment. There is no other way the con-rod bolt (that is in one piece) could have escaped its proper position unless its threads were stripped. By the look of things, the con-rod was in its unusual position upon disassembly (ie: assuming the mechanic didn't undo the unbroken bolt and remove the cap)
The Turbo exhaust outlet is fairly typical corrosion, that is the results from exposure to salt air. This is fairly common on pleasure boats that sit in marinas for most of their lives, and especially those that don't have a flapper or water trap and exit just above the water line.

IMHO

Allan.

Here’s the bolt close up. Looks to me it went for a bashing ride. Mechanic said he found it in the pan.
About the turbo: This sort of carbon build up is typical? OK...would like to hear from others about this, cause the dealer says this should be clean. As I said before, except for a few months, this engine has been operated several times a day for the past 16 months. At some point, almost every time we are underway, it gets revved in to the 2400 zone, so it would assume I would see black exhaust?
And, the boat never put out black smoke.
Anyway, I’m still confused how all these thousands of boat engines could keep running if water is so easily entered into the exhaust chamber...And I wonder how the corrosion on the elbow can add enough water to make a difference given that just a few inches downstream there’s all the salt water in massive amounts! I can see why the part should be inspected and replaced as the metal and the weld only last so long. At some point it’ll just fall off etc.

So next I will analyze the turbo more closely to see what was the nature if it before the failure.

[9intheafternoon]

Hey, sounds horrible! You must have been very unlucky, and as mentioned in other replies is suspect an underlying defect.
No engine should have any problems with being “pushed”. Just imagine the push loads on a car or 4x4 when engine braking!

[Phil Lovering]

Originally Posted by Hunterdog

Will do Phil. Thanks for offer!!!

I see the components are still inside the engine, if that’s so there’s probably serious damage to the casing and other components. Take lots of photos, and dissemble the motor, noting all observations, no matter how small. Particularly retain the oil and filter... the filter will show a lot of history. Once the engine is fully dissembled detailed inspection can begin.
Where are you based, as this will dictate if it’s worth sending the specific components to me for detailed analysis.
Cheers
Phil

[Recy]

Originally Posted by argonauta1

Max prop or other type of feathering prop is the way to go.

What difference would that make compared to a fixed or a folding prop?

[skipperpete]

Originally Posted by Hunterdog

Here’s the bolt close up. Looks to me it went for a bashing ride. Mechanic said he found it in the pan.

About the turbo: This sort of carbon build up is typical? OK...would like to hear from others about this, cause the dealer says this should be clean. As I said before, except for a few months, this engine has been operated several times a day for the past 16 months. At some point, almost every time we are underway, it gets revved in to the 2400 zone, so it would assume I would see black exhaust?

And, the boat never put out black smoke.

Anyway, I’m still confused how all these thousands of boat engines could keep running if water is so easily entered into the exhaust chamber...And I wonder how the corrosion on the elbow can add enough water to make a difference given that just a few inches downstream there’s all the salt water in massive amounts! I can see why the part should be inspected and replaced as the metal and the weld only last so long. At some point it’ll just fall off etc.



So next I will analyze the turbo more closely to see what was the nature if it before the failure.

Hi Hunterdog
That buildup on the turbo housing is heavy corrosion covered with a layer of soot and is reasonably common to see it occur when the weld on the mixer elbow flange corrodes away and allows raw water to enter the turbo at shutdown, sometimes a lot of water. The service life of that mixer elbow is very short, I think Yanmar suggest around 500 hrs.

[Hunterdog]

Originally Posted by skipperpete

Hi Hunterdog
That buildup on the turbo housing is heavy corrosion covered with a layer of soot and is reasonably common to see it occur when the weld on the mixer elbow flange corrodes away and allows raw water to enter the turbo at shutdown, sometimes a lot of water. The service life of that mixer elbow is very short, I think Yanmar suggest around 500 hrs.

Wow. This engine was serviced by a yanmar dealer in oct 2018 and again in June 2019.
I was planning to service again this month before heading back to the Med. I had hoped to find a good shop in Gran Canaria as there are so many boats that pass thru for the arc.

[sealife2]

Hi Hunterdog
i have experience with 4jh yanmars
the carboned up turbo is exactly what happens after approx 1000- 1500hrs... when run at lower rpm combined with no mechanical cleaning or every few hours hi rpm cleaning cycles as per yanmar maintenance/ operating instructions. it results in reduced power, reduced, rpm, little or no boost and excess carbon build up in the cylinder heads.
the one clean cylinder head section to me indicates a regular small amount of water being run through that cylinder... the water vaporizing when that cylinder fires removes the carbon over time its not a one gulp thing that cleans a cylinder head like that, as someone else mentioned.
given that one cylinder has most likely had water ingested regularly and the others are dirty it would seem the leak was into that one cylinder only... often a gasket leak or occasionally casting pin/ corrosion hole
it only takes a tiny bit of water to lock the cylinder. those motors can run with a bent rod bent/ rod cracked piston for a while . its possible that partial locking happened several times, it would be only a mater of time till something let go.
if someone had the head off and reused the old head gasket...leakage, is a common result.
the red stuff in the head cooling ports if rust likely means salt water in the coolant chambers fro a leak if it is RTV sealant someone already had the head off ...
the turbo flange connection discolouration also shows its had water sitting in there, most likely nothing new as it has crept under the gasket
the leaking mixer may have caused a problem but i think it is not likely the failure culprit as only one cylinder shows evidence of ongoing water ingestion.
perhaps your exhaust system isn't designed correctly but i would think that is not the main failure cause.
competent service would have caught the turbo and water issues much earlier in the cycle

BTW the new engines (common rail) require Very very clean fuel. For reasonable life make sure your filtering system is up to it.
Best of luck with the new install.

[Shaneesprit]

Hi
Well from what I see
Broken bolt and spread big end, the big end of the rod failed first - possible a Torque issue on build but you have 1200 hours so unlikely to be torque.
I don’t believe a top end failure caused the big end to fail, because I have seen and investigated a lot of failures and never seen the top end failure damage the Rod at the crank - I have seen the Rod bent due to top end failure but not splay the big end.
Looks like over speed to me - Engine runaway from diesel in the oil from running at low RPMs for 1200 hours. Diesels like and need to be used hard it’s even in the manual. Low load running causes diesel to flow down the cold bores into the oil raising the oil level and causing a runaway and possible over speed!
Like the oil level in the boat manual.
So you were on the vessel,
1) did the engine go with a BANG or did it Scream and BANG?
2) when was the oil last changed? and I mean you know it was actually changed - not the last time you paid for it to be changed?
3) get an oil sample analysis- see if it’s new oil - unfortunately they can’t analyse the oil grade.
But don’t worry about mixing oils there is no issue with that as long as the oil is suitable, they just don’t want to mix due to having you on their oil and reputation - it’s a Turbo engine? if the oil was wrong Turbo always fails first

[DougR]

Originally Posted by Hunterdog

Here’s the bolt close up. Looks to me it went for a bashing ride. Mechanic said he found it in the pan.

Nice photo of the rod bolt......but I wouldn't say it went for a " bashing" ride. More likely it went for a "grazing" ride. That is, as it was working its way out of the rod it grazed a few things. Perhaps it was some aluminum webs that are cast into the oil pan, or maybe some sheet metal bracketry that supports the oil pickup screen, or something like that.....something soft enough to mark the bolt head, but not substantial enough to bend the bolt. If you look at the pan or other bits that reside in the pan you will see the evidence of the contact. Of course the mechanic said he found it in the pan, because it was the first part that escaped the connecting rod.

If the fractured rod bolt had broken first, before the intact bolt worked itself out of the rod, the rod cap, the bearing shells, the journal, and the intact bolt would have been beaten to a pulp as the intact bolt worked itself out. But all of these things are basically intact, meaning they were in position and functioning right up to the point that the rod bolt broke and the engine stopped.

So the culprit in this mystery is the wayward rod bolt. Why did it loosen and back out of the rod? Maybe it wasn't torqued enough. Maybe it's material is marginal and it stretched and couldn't maintain the torque necessary to remain tight. Maybe it was over torqued, past the material yield point which allowed it to loose its strength and loosen. If you want to do some material analysis, here is the place to start.....IMHO.