(ENGINE RUNS!!!!) Broke down my engine block and changed the engine

[11_335D]

Looking at picture 2 and 3, you can see some gouging on the right stem(shiny part) compared to left stem. I'd still pull the head to know for sure, your valve may still be intact just slightly deformed.

Anyway the over revving theory may not be this case but still a possibility if you rev above and beyond design requirements(valve spring pressure) .

[Assimilator1]

Originally Posted by 11_335D

Sorry about your engine and all the "new" engines issues you are dealing with.

Based on your video and pictures you provided its seems like the failure mode was due to over revving. It seems you were definitely hanging in that gear longer than you should have. This caused "valve float" which allowed the piston to kiss/touch the valves(more than likely intake valves due to higher cam lift profile than exhaust). Once it kissed that valve, the valve either bends or breaks and your piston tries to compress it which it obviously can't and the weakest link in the rotating assembly...your #5 rod takes the compressive load and snapped instantly.

You can tell the event occurred so quickly because your crankshaft rod journal for number 5 looks amazing considering the forces it took. If this had happen at a lower RPM I don't believe your journal would look this good. Anyway this is just my assessment of what I think happen. Only way to verify is to remove head and look at the combustion chamber for number 5 or maybe look inside the intake or exhaust port for a broken/bent valve.

This doesn't sound right, I've had at least several engines apart where the cambelt/timing chain has broken or slipped, I've also seen many others with the same failure. Not one had a snapped rod, including ones which had severe piston damage, and no obvious sign of bent rods (not saying their wasn't a miniscule amount of bending though).

I think it's extremely unlikely that pistons hitting valves (even if a valve head has snapped off!) will bend (significantly) or break a rod, it will mash the head and piston tops of course though (especially with a broken belt or chain). And I think a piston kissing a valve will almost certainly not cause any notable rod bending, I'd put money on that .
Broken rods are more likely from e.g an extreme over rev exceeding the rods strength, or being bent from hydraulic locking, then possibly breaking. Also, apparently it's possible to break the rod if the rod bearing seizes (not something I've come across personally).

Originally Posted by jvictormp

Hi guys. Thanks for replies.

Just updating.

All other cylinders rod bearings looked exactly the same as number 1, which is: having an amount of damage in the center. I mean, all of them, seven rod bearings.
That leads us to think that after having the block broke, there was no oil pressure for some seconds before turning engine off.

So, for us to know, a few seconds without oil pressure are enough to damage the rod bearings.

Can't imagine the main ones.

I think this is a very likely scenario.

Btw, can you take pics of the broken rod? (what's left of it!)
There's a slim chance we might be able to see if it was broken by compressive forces or stretching forces.
FWIW, when I looked through all the engine failures in the 'blown engine thread', roughly 200 engines. Their wasn't a single case of an OEM rod breaking that didn't have other causes (like hydraulic locking, or seized rod bearing).

[jvictormp]

Originally Posted by Assimilator1

Btw, can you take pics of the broken rod? (what's left of it!)
There's a slim chance we might be able to see if it was broken by compressive forces or stretching forces.

Yeah, I can do that on monday. On weekends, my wife prohibits me from going into my garage

But today, piston's out!!!!

But, still there no sign of what the fuck happened.

Edit.: please disconsider all below in red, because as the manual said, I was probably at 1TDC overlap:

Yet, there was a problem of timing. When I put the timing tool on bank 2, #1TDC, admission wouldn't allow the tool to sit perfectly. Differently, bank 1 would.

So I guess there was a reinstallation of camshafts, and probably a failure in the timing procedure.

I had to remove first the exhaust camshaft bank 2, then turn the engine a little to align timing tool for admission correct point, then remove admission camshaft bank 2.

Okay, then I removed head from bank 2, and removed the piston.

It didn't show no signs of nothing. No hydrolock, no pre-ignition. Piston pin shows no sign of bent rod. Seems like it was just the the rod. Don't know why.

This engine has a 2011 block, but the car is 2008. May the crankshaft be a 2008, and not well installed in the 2011 block? Bad balanced?

[jvictormp]

What you guys think on the admission timing on bank 2? It was 1 or 2 degrees off.

Would that be a cause or effect?

[Ajolives]

Originally Posted by jvictormp

What you guys think on the admission timing on bank 2? It was 1 or 2 degrees off.

Would that be a cause or effect?

IIRC, think that's normal. The TIS says you have to rotate the cam with an open needed wrench to line up the exhaust cam lock.

[jvictormp]

Originally Posted by Ajolives

IIRC, think that's normal. The TIS says you have to rotate the cam with an open needed wrench to line up the exhaust cam lock.

Edit.: Found the TIS, it says you check bank 2 in 1 TDC position, then you do a 360º turn, stopping engine at Overlap 1 TDC, then you check bank 1. Now I think there was nothing about timing problem on this engine.

[Redd]

Your VANOS gear covers look pristine. Take out the 4 gears and sell them. They're worth 1k there.

[deansbimmer]

Originally Posted by jvictormp

What you guys think on the admission timing on bank 2? It was 1 or 2 degrees off.

Would that be a cause or effect?

That's what you'll find if the check sequence was incorrect. Perform it again per TIS instruction, it's probably fine.

[Assimilator1]

Originally Posted by jvictormp

Yeah, I can do that on monday. On weekends, my wife prohibits me from going into my garage

But today, piston's out!!!!

But, still there no sign of what the fuck happened.

Edit.: please disconsider all below in red, because as the manual said, I was probably at 1TDC overlap:

Yet, there was a problem of timing. When I put the timing tool on bank 2, #1TDC, admission wouldn't allow the tool to sit perfectly. Differently, bank 1 would.

So I guess there was a reinstallation of camshafts, and probably a failure in the timing procedure.

I had to remove first the exhaust camshaft bank 2, then turn the engine a little to align timing tool for admission correct point, then remove admission camshaft bank 2.

Okay, then I removed head from bank 2, and removed the piston.

It didn't show no signs of nothing. No hydrolock, no pre-ignition. Piston pin shows no sign of bent rod. Seems like it was just the the rod. Don't know why.

This engine has a 2011 block, but the car is 2008. May the crankshaft be a 2008, and not well installed in the 2011 block? Bad balanced?

Any pics of the broken rod then?

[jvictormp]

Pistons 5 and 6 pictures.

There are some marks in piston 5 head.

[jvictormp]

Originally Posted by Assimilator1

Any pics of the broken rod then?

Here we go.

[drrust]

Can you take pictures of the fracture surfaces?

[11_335D]

I still stand by my initial assessment. Looking at the #5 piston valve relief and crown area you can see the intake valve was kissed at least 3 or more times before the rod gave up. The intake valve is seated properly in the head currently, but I'm sure the stem is no longer true along with the valve guide.

Can you pull #5 intake valve and valve spring out. I guessing the valve spring may have failed(fractured, broke maybe a small portion of the coil).

[Assimilator1]

And seeing the very mild damage to the piston face (which might have happened after the rod broke), and no serious damage to valve heads, I'm certain now that valve to piston contact did not damage the rod in anyway.
If the valve heads had snapped off and were mashed into the cylinder head or piston, then maybe that would cause a rod to bend enough, and maybe break, but this isn't the situation.

jvictor
Thanks for the excellent quality photos again, sadly I see nothing obvious that might explain the break, but maybe someone with more experience will?
And drrust asks a good question, seeing the broken surfaces might provide some answers (sorry, we're asking for more photos! lol ).

[jvictormp]

Originally Posted by drrust

Can you take pictures of the fracture surfaces?

Yes, mate. See below.

Originally Posted by 11_335D

I still stand by my initial assessment. Looking at the #5 piston valve relief and crown area you can see the intake valve was kissed at least 3 or more times before the rod gave up. The intake valve is seated properly in the head currently, but I'm sure the stem is no longer true along with the valve guide.

Can you pull #5 intake valve and valve spring out. I guessing the valve spring may have failed(fractured, broke maybe a small portion of the coil).

You got a point, I'm curious for that, but I can't do it right now because I'm leaving to work for 20 days offshore and I'd need time to remove valves.

Originally Posted by Assimilator1

And seeing the very mild damage to the piston face (which might have happened after the rod broke), and no serious damage to valve heads, I'm certain now that valve to piston contact did not damage the rod in anyway.
If the valve heads had snapped off and were mashed into the cylinder head or piston, then maybe that would cause a rod to bend enough, and maybe break, but this isn't the situation.

jvictor
Thanks for the excellent quality photos again, sadly I see nothing obvious that might explain the break, but maybe someone with more experience will?
And drrust asks a good question, seeing the broken surfaces might provide some answers (sorry, we're asking for more photos! lol ).

I think a "rodless" piston would kiss (or be kissed) a valve only one time, and be moved down in a way that in the next cycles there would be no contact again.

If piston has got many marks, I guess valve and piston made several contacts when still having rod.

Unless the first break was near to the piston, leaving a "pistonless" rod moving up and down (and hitting piston sometimes), until it went somewhere between crank and block, breaking the second time near to the crank.




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You can see in those pictures the bank 1 head, and interestingly, cyl 1 (exact opposite to cyl 5) shows the same oily aspect on valves.

[drrust]

From the upper piece of the rod, the farthest shot shows a small semicircular area (by red line). Does it look smashed, or does it have fine lines following the semicircular shape? The blue area looks smashed to me.

The lower portion of the rod seems to have an overload structure. This would suggest that this broke later.

[Redd]

The pics of the bent rod and how it broke suggests a huge compressive force. I'm thinking hydrolock from a stuck open fuel injector.

[jvictormp]

Originally Posted by Redd

The pics of the bent rod and how it broke suggests a huge compressive force. I'm thinking hydrolock from a stuck open fuel injector.

Possible but not possible.

- No gas smell.
- No defect on bench tests of all the injectors.


But that happened once in that cylinder in 2019.

Maybe the bending happened that time?

A hydrolock now would only be possible if it was by oil, as there are signs of oil blowby in the spark plugs and valves.

[jvictormp]

Originally Posted by drrust

From the upper piece of the rod, the farthest shot shows a small semicircular area (by red line). Does it look smashed, or does it have fine lines following the semicircular shape? The blue area looks smashed to me.

The lower portion of the rod seems to have an overload structure. This would suggest that this broke later.

I'll try filming. I think you've seen something, but I'm not as knowledged on that to answer your question.

[jvictormp]

drrust

[11_335D]

Bingo on the "rodless" piston comment, I have the same view as you. I'm not sure why some "members" are critiquing my assessment when I've been pretty close on potentially finding a root cause. I would like to state I am by no means an EXPERT in engine building/failure analysis/mechanical engineering/etc but I do enjoy building high revving naturally aspirated engines as a HOBBY and have had my fair share of successes and failures. I enjoy contributing to the forum to help others but not to judge others contribution.

jvictormp, Thank you for taking the time to upload all the photos and videos, hopefully a root cause will be identified if not we all learn something from this.

[drrust]

Thanks for taking the video. It maybe a trick of the light, but that small corner (semicircular area) may indicate the presence of a fatigue crack. It's hard to tell for sure as much of the surface has post failure damage.