Broken Crank
- Thread starter Todd C
- Start date
punkmechanic
diesel tech
I dont know how you do that. that is amazing. a solid impact on a piston maybe? are any of the rods bent or do any of the pistons look impacted?
I saw a crank break on a bbc but that was blown and the dumb idiot put giggle gas on it ( i told him it would break something) 200 feet into the quarter hit lifted the front wheels, broke the pinion over revved and cracked a piston that in turn broke the crank. really cool to see. I had already been paid for the build up and I saw another 3 months of work and 4 figure check in my future
lol
flatlander
plays dirty when losing
Refresh my memory. Was it still running?
Went back through your posts. Now you know why all the front engine components had troubles as well, eh?
Went back through your posts. Now you know why all the front engine components had troubles as well, eh?
That is a fatigue crack I bet, the rod would bend before the crank would break, I would call that whole engine unusable. I would bet money the mainline on the block is now bad.
That really sucks. Was the ring loose on the balancer? That still wouldnt throw it out of balance, it could mess upo the dampening effect though. strange.
That really sucks. Was the ring loose on the balancer? That still wouldnt throw it out of balance, it could mess upo the dampening effect though. strange.
69dieselfreak
well that nice
1dieselman
Full Access Member
I've seen SBC cranks break and bent cranks in various diesels. The engine I have in my truck now the crank came out of a engine that had wiped out a rod, piston and cylinder and was unhurt. Sometimes high power hot rods will break the crank at the rear journal
Todd C
Full Access Member
Long story short - In september, while towing it started knocking, started to lose power and died. The injection pump shaft was broken. The harmonic balancer was bad. When a new pump and harmonic balancer were put on, it did run, but had a "knock" per the mechanic that was working on it. Oil analysis showed bearing problems. It's been sitting since, and I finally got the engine out, and just pulled the pan and crank today. I haven't pulled the heads but I don't expect to find anything major. Compression test was good.
So far, the block looks ok...
My best guess is that maybe the bad harmonic balancer caused the fatigue crack. But I'm hoping some with more experience will give me their opinion.
So far, the block looks ok...
My best guess is that maybe the bad harmonic balancer caused the fatigue crack. But I'm hoping some with more experience will give me their opinion.
1dieselman
Full Access Member
Get a good straight edge and .001,.002 feeler gauges and check across the main bearing saddles after you get all the bearings out.
sootman73
Registered User
i would take an uneducated guess and suggest a manufacturing process of the crank error. shouldn't that have a much more consistent surface where it cracked? looks like there was some contaminant in the metal when it was poured...?
NJKen
is a daddy!
Holy cow man
I guess I was wrong. That is the first IDI have ever seen with a busted crank. I would be a little suspicious of the block now as well. If you really want to re-use it you should have the main bores checked by a good machine shop. Preferably one that can line bore it if needed.
Ken
I guess I was wrong. That is the first IDI have ever seen with a busted crank. I would be a little suspicious of the block now as well. If you really want to re-use it you should have the main bores checked by a good machine shop. Preferably one that can line bore it if needed.
Ken
My guess would be that you had a bad harmonic damper for awhile and somehow water got into the fuel IP and caused the IP to break (hydro lock) and while the mixed fuel combusted in one of the cylinders, the drop of water 'flashed' into steam that resulted in a thousand fold charge of pressure, thus shearing the crank where the stress riser (created by the bad damper) sat.
That's the scenario that keeps playing over in my mind. I would think the block should be checked for other cracks, particularly along the casting flashes caused by the sand mold. If no cracks are found via magnaflux, then I would shotpeen the rest of the rods and the new crank also should be magnafluxed too.
Sorry about your luck, that is very rare on diesel cranks I would think...
That's the scenario that keeps playing over in my mind. I would think the block should be checked for other cracks, particularly along the casting flashes caused by the sand mold. If no cracks are found via magnaflux, then I would shotpeen the rest of the rods and the new crank also should be magnafluxed too.
Sorry about your luck, that is very rare on diesel cranks I would think...
david85
Full Access Member
Something went horribly wrong there. Thats 100lbs (guessing 100 or more) of forged, heat treated steel that broke.
This was a 7.3 remanufactured engine, right? I think I've only heard of one other case of a broken crankshaft. Also a 7.3 reman......
I suspect the main bearings are not lined up right strait, and the block might be warped causing the crank to flex. Line boring and oversize bearings might be able to fix that. Other option is to get a used 6.9 and overhaul that instead.
. Thats 100lbs (guessing 100 or more) of forged, heat treated steel that broke.This was a 7.3 remanufactured engine, right? I think I've only heard of one other case of a broken crankshaft. Also a 7.3 reman......
I suspect the main bearings are not lined up right strait, and the block might be warped causing the crank to flex. Line boring and oversize bearings might be able to fix that. Other option is to get a used 6.9 and overhaul that instead.
That is actually cast steel that broke.
IMHO it was a fault from day one that started the chain of events.
No. 1 there was a casting flaw caused by a cold shot or intrusion of impurities.
Attachments
The main thing is to get the block checked before going further. A good crank will be easy to find. And it needs to be crack checked not just straight checked. It will probably be ok, these are beefy blocks but one cannot be too careful
NJKen
is a daddy!
My guess would be that you had a bad harmonic damper for awhile and somehow water got into the fuel IP and caused the IP to break (hydro lock) and while the mixed fuel combusted in one of the cylinders, the drop of water 'flashed' into steam that resulted in a thousand fold charge of pressure, thus shearing the crank where the stress riser (created by the bad damper) sat.
That's the scenario that keeps playing over in my mind. I would think the block should be checked for other cracks, particularly along the casting flashes caused by the sand mold. If no cracks are found via magnaflux, then I would shotpeen the rest of the rods and the new crank also should be magnafluxed too.
Sorry about your luck, that is very rare on diesel cranks I would think...
Huh?
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