115 inline 6 locking up, then unlocks by simply wiggling flywheel up and down

joezek

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May 8, 2011
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I was idling along this morning and I heard a random clanking noise, each time the engine would stutter like it was missing. Then 5 min later this horrible high pitch scrape for half a sec, and it locked up. Got towed home pulled the plugs, one looked like it had rust or mud on it. I grabbed the flywheel and suddenly it was free. All 6 have compression, I put the plugs in, it ran perfect. 2 min later it randomly started making clanking noises, metal to metal contact somewhere. I noticed that the flywheel is moving up and down about 3/8", and is bolted tight to the crank. Whenever it moves up, it jams the engine. .....anyone every heard of this problem? Is there a thrust bearing that could have gone bad?
 

gm280

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Jun 26, 2011
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Sounds like the bearings are gone and allowing the crank to move...not a good thing. The metal on metal sounds like the throws are hitting bearing webs that support internal bearings... JMHO!
 

joezek

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it was stuck real bad, I grabbed the flywheel and turned it backwards about an inch, then started and ran perfectly for a few min....until BAM again
 

emckelvy

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Jan 16, 2004
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+1 on broken crank,usually below #1 journal..

Yup, years ago I had a 1350 that I picked up cheap 'cause it had a busted crankshaft the same way. Seen other ones break in the same manner. Guess it's a common weak spot in the crankshaft casting.

Time to pull the flywheel and upper bearing cap for a look-see. I bet the flywheel wiggles to-and-fro like mad, and the crank will move even more once the bearing cap is removed!
 

joezek

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if the crank is broken, how would I get compression on all 6 cylinders.....? If it's not broken, is there something I can adjust or replace that would eliminate the free play causing up/down movement? BTW, I've never heard another one of these engines in person, so I don't know what they sound like normally, but this one's real clanky and sounds like a diesel engine. Maybe it's the crank smacking into the block webbing....dunno.
 

flyingscott

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Apr 8, 2014
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If you have compression on all 6 spun bearing easy to check. Start at #1 turn the crank until the piston starts going back down stick a wooden dowel int the spark plug hole and push on the piston if it moves and you hear a slight clunk you found it. do that to all six
 

flyingscott

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I apologize if all those tests are good pull the lower unit off and see if that is the problem My computer keeps kicking me off
 

mlbinseattle

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Aug 1, 2015
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From what I understand, there are shims between the upper end cap and block and lower end cap and block. The amount of shims should be approximately the same to center each throw with the respective cylinder. The amount of back and forth end play should be within the engine's specs. You can still have compression on all cylinders with a cracked crank provided you can still turn the crank. But, that's what it sounds like to me ... a cracked crank ... probably a stress fracture that's expanding. If it's doing what you says it's doing, then it's definitely time to pull the crank and inspect it. 3/8" of an inch (.375") is a lot of end play. The amount allowed on my 850 is only .004" - .012" if that gives you any idea how bad .375" end play is.
 

joezek

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May 8, 2011
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137
I pulled the flywheel and upper cap, the upper bearing is kind of rusty, lots of free play. I don't know if it's replaceable, but I'm sure the other bearings are as bad or worse.
 

Chinewalker

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Aug 19, 2001
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8,902
It may even still run with a broken crank. They rarely break at 90-degrees. Usually they shear at an angle, and with the caps and mains all holding stuff in place, you can easily still turn the motor over. The crank parts meeting at an uneven break will still grab. Yours might be seizing because it eventually rides up and binds.
 
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