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Author Topic: #2 main cap broke on aaz  (Read 8224 times)

Reply #15September 27, 2011, 11:02:59 am

Mark(The Miser)UK

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Re: #2 main cap broke on aaz
« Reply #15 on: September 27, 2011, 11:02:59 am »
Same thing happened to me but on cap #5. Split in half. And the cap pieces got stuck between the crank weights and the block and left a big hole as a result, just behind the starter.


Well that doesn't count; it's merely an extra blowby vent ;D

Sorry I couldn't help myself :'(
Mark-The-Miser-UK

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I'm not here to help... I'm here to Pro-Volke"

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Reply #16September 27, 2011, 11:44:03 am

vanbcguy

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Re: #2 main cap broke on aaz
« Reply #16 on: September 27, 2011, 11:44:03 am »

And #2 main cap gone.
I found both pieces of the cap as well as both cap bolts in the engine bay.  I haven't uploaded those pics yet.  Coming soon.

That ALMOST looks like the #1 rod twisted off and sticking down between the counterweights?  What's going on there?
Bryn

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Reply #17September 27, 2011, 12:42:47 pm

CRSMP5

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Re: #2 main cap broke on aaz
« Reply #17 on: September 27, 2011, 12:42:47 pm »
i think it was the putter that poked the hole with cap parts..

Reply #18September 27, 2011, 02:20:59 pm

Sierra94

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Re: #2 main cap broke on aaz
« Reply #18 on: September 27, 2011, 02:20:59 pm »
410: No, I only found half of it in the pan along with the 2 bolts (which were undamaged!!). The other part of the cap is still missing ;D

This happened a couple of years ago, and at that time I only took pics of the outside damage. I swapped the extra vented AEF (1.9 NA) for a 1Z and built a m-Tdi IP that I still run today.
<-- My M-tdi Mazda B-1800 and my other cars

Reply #19September 27, 2011, 04:14:50 pm

410

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Re: #2 main cap broke on aaz
« Reply #19 on: September 27, 2011, 04:14:50 pm »
Like I mentioned before, this engine still ran.  All rods were completely intact.  #2 rod did suffer some damage but I didn't notice until I removed it from the block.  #1 piston also had a bit of its skirt broken off as well.  All bearings aside from number 2 main cap were intact and believe it or not, the crank is in reusable shape.  So, I guess I'm out one block, one rod and one piston. ;D
Toyota truck 4x4 with Mtdi, M-vnt gt1749va, 11mm pump, fmic, smog .216 nozzles.  Sold!
Working on 1993 4runner mtdi, gtb1756vk, 11mm pump, smog .216 nozzles, custom 1" thick adaptor plate, pd150 intake manifold.

Reply #20September 29, 2011, 08:43:16 pm

410

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Re: #2 main cap broke on aaz
« Reply #20 on: September 29, 2011, 08:43:16 pm »
Okay, here's some pics of the cap and bolts.  After looking at everything a little closer, it does look like one of the bolts broke first, then the cap. The cap then breaks the remaining bolt at which point everything got ejected.

If you look closely at the break on the bolt on the left, the fracture shows signs of fatigue where the right side bolt was a clean break. 

Mark, I would have to agree with you that this bolt was probably overtightened eventually leading to the failure of the bolt.  Either that or the bolt was flawed but I doubt that.
Toyota truck 4x4 with Mtdi, M-vnt gt1749va, 11mm pump, fmic, smog .216 nozzles.  Sold!
Working on 1993 4runner mtdi, gtb1756vk, 11mm pump, smog .216 nozzles, custom 1" thick adaptor plate, pd150 intake manifold.

Reply #21September 30, 2011, 04:35:11 am

Toby

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Re: #2 main cap broke on aaz
« Reply #21 on: September 30, 2011, 04:35:11 am »
This kind of damage is typical of a kickback when starting a motor on ether. I have seen this a number of times and ether has always been the culprit.

Reply #22September 30, 2011, 10:06:30 am

Mark(The Miser)UK

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Re: #2 main cap broke on aaz
« Reply #22 on: September 30, 2011, 10:06:30 am »
 Having  done some reading; I have discovered that the fracture profile of those bolts are of flexing fatigue.
 
Clearly the left bolt went first and for some unknown period of time hammered together, strange in itself as it should have dropped out.


Not clear on the pic but the bolt face proably simulates a scallop shell, with the hinge spot being the actual last cling of bolt.
Where there are no concentric rings with their centre at the hinge, signifys a relatively rapid fracture. like the right hand bolt.

Conversely circular waves/ripples would have signified a gradual flexing failure due to a repeated lower force.


Pure shear in anything other than a guillitine  effect in a very tight and close fitting pair of holes will result in a significant 'down the side' portion.  
Pure stretch will result in more of a crystalline effect not unlike the snapped cap.


Are the cap faces perfectly flat? [looking for a source of rocking under load]  

A picture of the shell bearings will tell much as they are so soft, and could tell you if it was a flexing crank, or bending conn. rod etc

I could of course be wrong, in all but the last paragraph ;D
« Last Edit: September 30, 2011, 12:54:24 pm by Mark(The Miser)UK »
Mark-The-Miser-UK

"There's nothing like driving past a bonfire and then realising; its my car on fire!"

I'm not here to help... I'm here to Pro-Volke"

Be like meeee: drive a Quantum TD
 ...The best work-horse after the cart...

Reply #23September 30, 2011, 07:39:32 pm

410

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Re: #2 main cap broke on aaz
« Reply #23 on: September 30, 2011, 07:39:32 pm »
The bearing on number 2 cap was squished into a ball. 
Toyota truck 4x4 with Mtdi, M-vnt gt1749va, 11mm pump, fmic, smog .216 nozzles.  Sold!
Working on 1993 4runner mtdi, gtb1756vk, 11mm pump, smog .216 nozzles, custom 1" thick adaptor plate, pd150 intake manifold.

Reply #24October 01, 2011, 12:43:08 am

Smokey Eddy

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Re: #2 main cap broke on aaz
« Reply #24 on: October 01, 2011, 12:43:08 am »
good god this is some most unfortunate carnage pics. Especially after just changing my main and rod bearings last week...
I think im gonna change my re-used (three times now) bolts for some 12.9 ...
Ed
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