Diagnosis: broken con rod

Skrilex

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Okay fellas I got the oil pan off and see what caused the ventilation that the previous operators gave me. Broken con rod. So, what’s next? Is this a case of- toss it entirely? Pull heads and look for cause? Or ? I haven’t dealt with many of these so I’m not sure what the standard approach is. I see no other obvious damage but I know some heavy damage isn’t always obvious. This is a 6.5 engine and seems to be nearly new

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NDT

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Pull it and do a cost analysis between fixing what you got and installing a tested 6.5 HMMWV pullout from various vendors. Any number of reasons for the broke rod. Army loves to drive through bodies of water and the slosh rides over the hood to the air intake.
 

Skrilex

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Reading that injector can go haywire and over fuel to the point of hydro? And of course a head gasket could cause hydro. These seem like the two most likely causes with a possible third option of a valve seat crack that allowed coolant to enter and hydro, but I wouldn’t think a small crack like that could cause enough water to hydro that hard.
 

Skrilex

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Pull it and do a cost analysis between fixing what you got and installing a tested 6.5 HMMWV pullout from various vendors. Any number of reasons for the broke rod. Army loves to drive through bodies of water and the slosh rides over the hood to the air intake.
Ah that’s true good point. Direct inhalation. I should also add that I have a used mystery motor 6.2 from a pickup sitting on shelf that could be cannibalized for this as well. Maybe strip it down, swap over all the tidbits that are newer over to it and try it out.
 
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Skrilex

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Looks like a fine time for an LS swap!


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gah that would make too much sense! Still kicking myself for not purchasing a duramax swap kit I found in CL for $2000 a few months back. I was all cummins focused at that time. Of course I’d like to just swap in a con rod and try it but that’s probably just the ADD talking.
 

Skrilex

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Looked a little closer at this and decided to pull the glow plug on that jug and it looks very clean, barely used.
This is the #3 piston btw. Also, interestingly I noticed black oil drips on everything in there, cam, piston skirts etc. so, that led me to think that this motor was very recently blown up, which surprised me for some reason. I had assumed it blew up a while back and was then relegated to parts-pig for who knows how long. The piston is about half way up the jug, and from what I can see the cylinder has no damage. The whole center section of the rod is gone, like, really gone. Must’ve left through the hole in the pan, so it doesn’t seem like it was flopping around maiming stuff for very long at all, as I can’t see any evidence of that. So, now I’m really curious what the piston and cyl looks like.

Thinking back to what NDT said I’m wondering if it was a big gulp of water, although that seems to bend them more often than break. The big end is smoothly lubed on the crank so it wasn’t a seize there.

Another lead east was broken injector dumping a lot of fuel in there.

Im not finding a lot on broken rods on these engines. One fella that seemed to work on a lot of 6.2 said he’d never seen one hydro from head gasket it was always either ingested lake water or broken injector fuel flooding. This is odd since I once had a 6.2 pickup that hydrolocked and it wasn’t fuel or lake water so I assumed HG.
 

gimpyrobb

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How far down does the piston go in a normal stroke? If it doesn't reach, I wouldn't think its a gonner.
 

jackson76550

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excessive rpm, abuse, or just a plain ol defective connecting rod are very likely. I just cant see an injector doing it, I have worked on plenty of diesels with stuck injectors that never came close to locking up....although none were 6.5/6.2. hydrolock would certainly bend a rod. bottom line..... you will never know what happened. to be on the safe side you could bench test the injector with the correct equipment, or just buy a new set for peace of mind.

personally id scrap the block if that rod did a little beatdown on the lower part of the cylinder. these engines are cheap enough I wouldn't bother trying to save one
 

Skrilex

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How far down does the piston go in a normal stroke? If it doesn't reach, I wouldn't think its a gonner.
It appears the Pistons bottom edges actually extend past the end of the jug into the sump by a little bit, so they would for sure be crossing this area many times a second. Maybe still okay but given the violence of the event and the mystery surrounding the cause I think it's only prudent to scrap it. Especially since I have a used truck 6.2 sitting here hat can go in. It's also a mystery, but at least it doesn't have holes in it!
 

Skrilex

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excessive rpm, abuse, or just a plain ol defective connecting rod are very likely. I just cant see an injector doing it, I have worked on plenty of diesels with stuck injectors that never came close to locking up....although none were 6.5/6.2. hydrolock would certainly bend a rod. bottom line..... you will never know what happened. to be on the safe side you could bench test the injector with the correct equipment, or just buy a new set for peace of mind.

personally id scrap the block if that rod did a little beatdown on the lower part of the cylinder. these engines are cheap enough I wouldn't bother trying to save one
Apparently the injector can break and it dumps a lot of fuels in. Not just stuck open. This is a new one to me also, but it sounds plausible.
But doesn't the injection pump control top speed? So how can excessive speed be a cause? Unless these engines are not able to handle the speed that the injection pump can dish out?
 

porkysplace

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It appears the Pistons bottom edges actually extend past the end of the jug into the sump by a little bit, so they would for sure be crossing this area many times a second. Maybe still okay but given the violence of the event and the mystery surrounding the cause I think it's only prudent to scrap it. Especially since I have a used truck 6.2 sitting here hat can go in. It's also a mystery, but at least it doesn't have holes in it!
Still a lot of good parts on it .
 

Skrilex

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Still a lot of good parts on it .
Ya that's true I'll just take the long block from the 6.2 and swap a bunch of stuff on it. From what I'm reading the 6.2 gets a noticeable improvement in fuel economy too over the 6.5.
Is there anything I'll need to know about all that before beginning transplant? One thing I'm planning is to graft the banks turbo on the side of the 6.2. So, I need oil feed and drain. A lot of installs have the drain going back to the fuel block off plate where the mech fuel pump was, but it looks like m998 still uses the mech fuel pump so can I still use that area or is there another drain spot I can use? Or should I go find an electric fuel pump and eliminate the mech?
 

papakb

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I had to chuckle about your comment on "noticeable improvement in fuel economy". From 10.5 mpg to 10.52mpg? LOL Your never going to get an environmentalist to look favorably on one of these vehicles.

 

NDT

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If your 6.5 is a GEP, then it is worth it to see if your machine shop can sleeve the damaged hole. Ancient GM 6.2s are not worth fooling with.
 

Skrilex

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I had to chuckle about your comment on "noticeable improvement in fuel economy". From 10.5 mpg to 10.52mpg? LOL Your never going to get an environmentalist to look favorably on one of these vehicles.

I dunno, some people claim pretty good mileage out of them, in grandpas truck. I don't subscribe to the theory of "it will never get good mileage so why even discuss it" theory. I mean, is 1mpg noticeably worse than 10mpg? They all count. But you're right, even if it got 72mpg the Subaru driving public will still sneer at me rolling by. Luckily I give zero clucks about that.
 

frank8003

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Skrilex;2085517 ~ said:
I dunno~ they will never get good mileage so why even discuss it" theory.~
~ Luckily I give zero clucks about that.
My Roadmaster does an honest 10mpg whatever I put in it.
Last hurricane I was laughing at all the pickups lined up to get sheets of plywood that didn't fit in their trucks. I just put it all inside.
Always buy/run a vehicle for what it can do for you.
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Skrilex

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My Roadmaster does an honest 10mpg whatever I put in it.
Last hurricane I was laughing at all the pickups lined up to get sheets of plywood that didn't fit in their trucks. I just put it all inside.
Always buy/run a vehicle for what it can do for you.
View attachment 711512
Well I'm not sure what a hmmwv will do for me lol. I really have zero use for one. I have a pickup that holds plywood, a ute that gets 24mpg, and a sports car that gets 30 mpg. People say the hmmwv is good off road, but around here I think it would be a little large. We off road on roads that look more like overgrown animal trails a lot of time. But, who cares it's cool and I'll enjoy rolling around in it.
 
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