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  #73  
Old 11-21-2010, 11:09 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Assuming that the OP is telling us the whole story and telling us the complete truth, there's also the possibility that the connecting rod was defective. Remember, this is a new vehicle will low mileage on it....and something like a defect in a cast connecting rod may take a bit of time before an issue manifests. What if the dealership mechanics found a trace of water from the puddle the guy drove through, and just assumed hydro-lock cause the rod to snap?

Another point to consider-- how do they explain the absence of water in the other 5 cylinders? Surely they would have looked for it right away.
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  #74  
Old 11-21-2010, 11:11 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Quote:
Originally Posted by Marlin View Post
Looks to me like the conrod could possibly swing 360 degrees around the bid end journal to make that hole.

Take another look at the first pic in post #68 MSCA, it's very bent, in a few spot, ie down near the big-end, then in the middle, then again toward the top. She's a piece of spaghetti!
Yeah, I definitely see the wavy bends you're talking about, but I've seen connecting rods that were bent like 25-30 degrees before they snapped. You're probably right that it swung down and pierced the pan. That makes sense.
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  #75  
Old 11-21-2010, 11:11 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Wow. Rod bent then snapped. I can see the bend in the photos assuming it isn't camera distortion. That does indeed match either a hydro lock or pre-ignition failure (Not detonation "ping"...but real, true pre-ignition timed way BTDC). The big question is HOW did either enough liquid get in there or did it pre-ignite way earlier than BTDC? It is possible the rod had a bad casting, but if that were the case I would expect the top of the piston to have smashed the valves and not have the rod look so bent on both sides of the breakpoint.

Sorry to say, but these images do suggest a liquid (water or coolant) got into the intake aft of the air filter and only affected this one cylinder. Is there any coolant leakage from the head at that cylinder location? That would do it; I've seen and rebuilt a few engines where the head gasket failed near an intake runner to the same effect we see here. If it was liquid, HOW did the liquid GET to that cylinder is your investigative task. I wouldn't disregard a pre-ignition event either but that would be a rare/remote possibility in a properly running, modern, computer controlled engine.
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Old 11-21-2010, 11:25 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Addendum:
MSCA I'm in agreement with your comment and it made me think about this further...If the rod had a defective cast that could account for the somewhat clean break, at its weakest point no less, and the mild bending we see may be stress-caused which lead immediately to the rod snap. These small displacement engines are putting out more than 1hp/cubic-inch and also more than 1ft-lb/cubic-inch so there are tremendous pressures on the pistons and rods. More stress than on larger displacement engines and zero margin for combustion errors due to liquids or a bad ignition event. If the casting was bad, this failure could be due to that and not liquid. The isolated existence of liquid only for this cylinder, however, is a mystery.
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  #77  
Old 11-21-2010, 11:29 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Yeah, the plenum pic does appear to show evidence of liquid while the air box shows no sign of muddy water. Any pics of the air filter, top and bottom as well as inside the tubing after the air filter?
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  #78  
Old 11-21-2010, 11:30 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

To help try and rule out hydro-lock, I'd like to see good detailed pictures of other cylinder's valves in comparison.
With the massive pressure of a hydraulicing engine, it's usual for the valves to be somewhat "indented" to want for a better term, ie, the valves are pushed further into thier seat.
Was there any damage to the valvetrain? Do these engines run a rocker arm of sorts or do the cams actuate directly upon the valve?
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  #79  
Old 11-21-2010, 11:48 PM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Do you see the color of the cylinder head, this engine has been run awhile with the piston not moving causing a lack of power due to a miss.
I have seen water build up in intakes from the exhaust gasses backing up in the intake from the moisture in the fuel.
This could of ingested enough water into the one cylinder to bend a rod but not stall the engine depending on how the intake contribution is placed, was this the first one in the intake sequence ?
Only one bent rod brings me to my conclusion.
37 years of experience and have seen this before.
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  #80  
Old 11-22-2010, 12:06 AM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Quote:
Originally Posted by emptypockets View Post
Do you see the color of the cylinder head, this engine has been run awhile with the piston not moving causing a lack of power due to a miss.
Wouldn't that have generated an error code?
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  #81  
Old 11-22-2010, 12:12 AM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Yes it would generate a code.

And I don't agree it's necessarily been running without the piston moving, but I agree it certainly hasn't been firing properly.

That could be from a number of reasons, even low compression caused by a "short" ie, bent, conrod.
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  #82  
Old 11-22-2010, 12:17 AM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Maybe, but in years past I remeber pcm update flashes to keep the light from coming on. Its all in the program, if the 3.6 showed a miss due to the computer being to sensative that a tsb fash would happen, just like ford 5.4 you can feel a miss but no light.
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  #83  
Old 11-22-2010, 12:21 AM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

In different tread regarding WK2 vs 3 years old BMW X5 I posted at the end of my reply this:
"Jeep has great interior/exterior. But I hope they are not using cheap China steel to build all the mechanical parts."
The reason I have mentioned is the conversation I had with my friend.
He works in CNC machine shop that makes water pump and trany details for GMC and Chrysler. They are getting rough pre-cast and making the fine detail on the CNC. I was very exided about the new Jeep, like all of us in this forum, and have mentioned to him that I am looking for reason to upgrade my '04 WJ with WK2. He told me that if I can see the pre-cast material they are getting, most with micro holes, I would never think about buying one. After that I have decided to wait for now. It would be very bad if he is right and bad material is reason for this breakdown. Really hope this is a single case.
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  #84  
Old 11-22-2010, 01:17 AM
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Re: 2011 Jeep Grand Cherokee 3.6L Pentastar V6 BLOWN-UP ENGINE!

Quote:
Originally Posted by Marlin View Post
Looks to me like the conrod could possibly swing 360 degrees around the bid end journal to make that hole.

Take another look at the first pic in post #68 MSCA, it's very bent, in a few spot, ie down near the big-end, then in the middle, then again toward the top. She's a piece of spaghetti!
Most of the stress on that rod seems to be on the weakest point though, thus making me believe that the it may be a manufacturer defect and not hydrolock

Quote:
Originally Posted by MSCA View Post
Assuming that the OP is telling us the whole story and telling us the complete truth, there's also the possibility that the connecting rod was defective. Remember, this is a new vehicle will low mileage on it....and something like a defect in a cast connecting rod may take a bit of time before an issue manifests. What if the dealership mechanics found a trace of water from the puddle the guy drove through, and just assumed hydro-lock cause the rod to snap?

Another point to consider-- how do they explain the absence of water in the other 5 cylinders? Surely they would have looked for it right away.
That's what me says as well.

OP did they find any water in the other cylinders, also can you get us a pic of the valves ?

Quote:
Originally Posted by dsi jeep View Post
In different tread regarding WK2 vs 3 years old BMW X5 I posted at the end of my reply this:
"Jeep has great interior/exterior. But I hope they are not using cheap China steel to build all the mechanical parts."
The reason I have mentioned is the conversation I had with my friend.
He works in CNC machine shop that makes water pump and trany details for GMC and Chrysler. They are getting rough pre-cast and making the fine detail on the CNC. I was very exided about the new Jeep, like all of us in this forum, and have mentioned to him that I am looking for reason to upgrade my '04 WJ with WK2. He told me that if I can see the pre-cast material they are getting, most with micro holes, I would never think about buying one. After that I have decided to wait for now. It would be very bad if he is right and bad material is reason for this breakdown. Really hope this is a single case.
Now that you said that this makes me believe what others have states that this indeed is a manufacture defect.

If you note the breaking point on that rod it's on the weakest part, and mentioned earlier that these engines are producing more than 1hp/in^3, the bends seem to be over time and the break happened after the rod bent too much.

Hmm ...
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