What years are the same? When did they change? Because to me it sounds like no year is more common then another.
Broken Crankshaft Count?
- Thread starter EDP
- Start date
What years are the same? When did they change? Because to me it sounds like no year is more common then another.
do all those cummins engines out there have trouble with their oil breaking their cranks under heavy abuse? do they have the same problems? 42 broken duramax cranks on this site alone is huge, imo.
i may have some new info to post.... stay tuned.
i may have some new info to post.... stay tuned.
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the cranks may be different, but who made the cranks? also, were the lb7/lbz cranks actually different in the area that breaks?
ok, so i went out and took another look at the crankshaft that broke. bear with me, it's been a year since i tore it down...... lol
the #2 main DOES have some surface irregularities. i blasted it with brake cleaner and wiped it down real good and took some pics. one of the things i began to think about was how that main cap had distorted, the bearing clearance would have been very small where the 2 bearing shells met together, basically scraping the oil off the journal. so i went out to take another look. after cleaning it off real good, here is what i saw.
the #2 main DOES have some surface irregularities. i blasted it with brake cleaner and wiped it down real good and took some pics. one of the things i began to think about was how that main cap had distorted, the bearing clearance would have been very small where the 2 bearing shells met together, basically scraping the oil off the journal. so i went out to take another look. after cleaning it off real good, here is what i saw.
Attachments
What are the chances the damage was done after the crank broke? If you look close it looks like the worn area is mostly on one side of the bearing surface.
this is possible. my main focus was the pitting. you can also see that little spot of blue, too. i am ASSuming i quickly checked that bearing and didnt see anything out of the ordinary, but i bet there was some funkyness going on at its edges.
could the cap have distorted before the crank let go? hmmmm...
super diesel
<<<< Under Pressure
I've seen spun mains on Cummins from over temped oil (what I use to build in the 90s). I've also seen it on 7.3 Powerstrokes, 6.9 & 7.3 (pre-Powerstroke), some Volvo and Renault diesels as well. These are not those diesels though. Bulletproof Diesel has a cooler out for the Powerstrokes. The bottom of these motors are only cooled with the factory heat exchanger. There is no extra way to cool the internals or lower section. What was your oil temps before it happened or even your oil pressure?
The factory doesn't install oil temp gauges or EGT gauges. How many trucks on this site has burned holes in the pistons or melted them even with a EGT gauge to watch? Some had a stuck injector but not all. Doesn't mean it's a problem with the way the motor was designed (some were cheaper material but were certainly working out of there design parameters). But that has nothing to do with the cranks spinning bearings (which has been common as well) or with broke cranks. I'm just taking a logical approach to the problem to help resolve it. Doesn't mean it's the total reason for all of them. I think the main gauges we need to focus on is a EGT gauge and an oil temp gauge. The fun gauge (boost) can fill in. I'm just taking a logical shot in the dark at this problem just like the rest of us.
Far above normal or acceptable heat would make the cap distort. Look at the locating fingers on the bearings to see if there still in good shape and wasn't the source. Hope you get it figured out.
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not 100% sure of what the previous owners did with my truck before she let go, just going off of what they told me. it was a repo truck with a self-loading wheel hauler bed. i would tend to believe they beat on it pretty good, but it was unmodded. the extent of hauling was pulling cars around, so figure around 3k lbs or so on the usual haul, maybe 7-8k if it hauled the occasional diesel dually, and the other half of those miles were empty with no car. it operated in a pretty flat area, no mountains or big hills. not a real big load on it, i wouldnt think.
i would honestly like to know what made the cranks break, because at this point i feel like the used crank i am putting in the truck now may let go at any time. i am not confident in this engine the way i would like to be. i wouldnt want to get stranded 2-300 miles from home pulling a race car home at midnight. also, its very expensive to rebuild one of these things, lots of work to get it out of the truck and on an engine stand, and tons of parts to keep up with on it. if i knew a way to avoid another broken crank, i would do it.
on the oil temps- of the people who have gauges, what sort of temps are they seeing? i am relatively new to the diesel stuff, so i am not sure on that. do they run that hot? im assuming the turbo is heating the oil? i still wouldnt have thought the oil got that hot in these things....
egt- what is the egt normally in a stock lbz?
Add a broken internally balanced LB7 crank to the list, pulling it apart tomorrow. Second crank this truck has broke at the 850hp range.
Truck does have a procharger though, so thats the likely cause, but sounds like the owner doesnt want to give up just yet. One more idea to try out. Thankfully the motor has a custom Extreme Engine Development crank support on it so major damage was avoided.
Truck does have a procharger though, so thats the likely cause, but sounds like the owner doesnt want to give up just yet. One more idea to try out. Thankfully the motor has a custom Extreme Engine Development crank support on it so major damage was avoided.
super diesel
<<<< Under Pressure
OO! I'm sure you'll never know what it was actually put through. As for the oil. What brand was it and change intervals? You can read some of the "oil cooling" thread to get an rough idea of what has been seen on our trucks and it varies. I would be worried about the journal web in the block and it's distortion from the outside to the inside of the mating surfaces. This area has a tendency to slope (warp inward) after this happens or if black residue is noticeable in the journal area on most blocks I've measured. If it's running good then leave it till it goes again (if it ever does, and it might be ok in which hopefully it is). I would think about installing an oil temp gauge some time just to keep it in check (all info on this and the location to put it is in the "oil cooling" thread). It only takes once and it's oil is compromised, and most keep driving them unknowing that it's oil quality is compromised. Like I said, it may not have been the cause. But an ounce of prevention may save it one day from another disaster that is easy to avoid. Protect your self and your investment.
super diesel
<<<< Under Pressure
So sorry to hear. Take pics and upload here if you can. Look for black residue around the journals, but then again could have just been to much pressure on the snout. Hard to say at this point.
Michael,
The fractures are bending fatiuge, slow growing crack overtime. You can tell by the beach marks or waves that radiate away from the crack initiation site. I have Bhowards broken crank and have a cat large engine engineer coming to Fairbanks to over see some engine work I will be doing on the new C175.
Anywho he is also a metallurgist as well. I have some ideas on this and want his opinion as well before I post my findings. I will start another thread with my theories and his for discussion.
Albert
Oh, I also agree with not being able to see a flaw or inclusion. Sometimes you need to look under a microscope to see what is happening as well...
super diesel
<<<< Under Pressure
Let us know your findings Albert. I know what your saying about the microscope. I used one for over 20 years troubleshooting and welding failed tool steels as a toolmaker. That's how I got to be so fond of the Metalax system. Hopefully we can put most these failure issues to bed here soon. It's not a good thing that's going on and is costing folks a lot.
The day mine broke it was about 20 degrees (F) out, started it and it ran for about 10 min before I drove it. I think it started to happen about 20-30 feet into the drive as I heard a tic tic tic. guessed it was a belt or tightener bearing. 13 miles later it quit but not before some pretty bad knocking and banging...... Oil was always changed at dealer as soon as it was needed. Anybody had an x-ray of a break done yet ? Mine will as soon as its tore down.
super diesel
<<<< Under Pressure
I guess what I need to say is, I don't have a bunch or even one broken crank sitting here to diagnose. I can only make an educated guess off of what I see in the pics.
I can offer this though. There is proof that oil and it being degraded can and will cause issues with the mains. I have proof through my own tests that this can be and is an issue on these trucks. How many have had fluctuating oil pressure gauges? This is no proof but tends to tell that there is something wrong. Were the pressure gauges being monitored closely? Doubt it. How many have been keeping tabs on the oil temp gauges during the life cycle of the oil that is being used (and for those that actually have a good accurate gauge)? The oil could be compromised long before the issue occurs. It's may be a case of the straw that broke the camels back.
I'm not trying to discredit anyone here, I'm just offering the proof that I have at this point that can and has been a source of the problem or a contributor to it logically. There could be other issues as well that will rear there ugly head in the future. I'm just trying to remove one of the known and proven factors that causes lower end failures that can be ruled out if proper steps are taken to protect in this area and prevent an easily avoidable bad situation for some folks. We need more solid info to truly diagnose these issues.
Maybe a new thread is in order? "How many broken cranks or spun mains on trucks that have oil temp gauges and have kept the oil temp under 240*F for it's life cycle?"
I'm sure we wouldn't eliminate it altogether, but I truly believe we would see a lot less failures if this was the case. I'm convinced this was mine.
Are dry starts having anything to do with it?
I can offer this though. There is proof that oil and it being degraded can and will cause issues with the mains. I have proof through my own tests that this can be and is an issue on these trucks. How many have had fluctuating oil pressure gauges? This is no proof but tends to tell that there is something wrong. Were the pressure gauges being monitored closely? Doubt it. How many have been keeping tabs on the oil temp gauges during the life cycle of the oil that is being used (and for those that actually have a good accurate gauge)? The oil could be compromised long before the issue occurs. It's may be a case of the straw that broke the camels back.
I'm not trying to discredit anyone here, I'm just offering the proof that I have at this point that can and has been a source of the problem or a contributor to it logically. There could be other issues as well that will rear there ugly head in the future. I'm just trying to remove one of the known and proven factors that causes lower end failures that can be ruled out if proper steps are taken to protect in this area and prevent an easily avoidable bad situation for some folks. We need more solid info to truly diagnose these issues.
Maybe a new thread is in order? "How many broken cranks or spun mains on trucks that have oil temp gauges and have kept the oil temp under 240*F for it's life cycle?"
I'm sure we wouldn't eliminate it altogether, but I truly believe we would see a lot less failures if this was the case. I'm convinced this was mine.
Are dry starts having anything to do with it?
I have NO doubts the oil is breaking down. In my opinion we don't have enough total volume of oil circulating and what's in there does not properly get cooled (inadequate).
That being said, on engines with much less robust cranks I've seen mains that were oil deprived and/or beat to death with too much compression and/or preignition or oil starvation and the cranks/blocks/bearings were all beat to hell yet the crank remained in one piece. While there are definite signs of oil fatique and lack of proper lubrication on the bearings (which needs to be addressed regardless), I just can't see how that is tearing the cranks apart like they are. Even severely abused motors with spun bearings have cranks that survive in other platforms...
That being said, on engines with much less robust cranks I've seen mains that were oil deprived and/or beat to death with too much compression and/or preignition or oil starvation and the cranks/blocks/bearings were all beat to hell yet the crank remained in one piece. While there are definite signs of oil fatique and lack of proper lubrication on the bearings (which needs to be addressed regardless), I just can't see how that is tearing the cranks apart like they are. Even severely abused motors with spun bearings have cranks that survive in other platforms...
in your opinion, how much oil would a stock duramax with no mods or tune need to stay properly cooled?
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2425542
this guy did an oil analysis on his '07 duramax after nearly 9k miles pulling a 15k lb trailer in the 115 degree arizona heat and it came out great.
if that didnt kill the oil, what would?
this guy did an oil analysis on his '07 duramax after nearly 9k miles pulling a 15k lb trailer in the 115 degree arizona heat and it came out great.
if that didnt kill the oil, what would?
super diesel
<<<< Under Pressure
In my opinion (I know it's not asked) it would be 10 qts. Anyone remember what the deep Allison pans did for the trans? Nothing. Just delayed the temping issue. What was the solution? A bigger, better cooler.
super diesel
<<<< Under Pressure
The only thing I could see was mineral content. How did he tow? Was it easy towing or pedal to the metal towing? What did his oil temps get to? He states he's using synthetic which is the choice to make in these conditions to add a bit of safety to the oil durability.
Anyone feeling the oil temps is a bunch of smoke being blown should feel free to ignore the oil cooling idea and keep on there marry way. Good luck. This is only for those who know what this can do to a motor. It only takes once.
Not sure why some cranks are breaking and others are holding together even after a spun main like in my case. I don't want to go back down that road again anytime soon to research it either. I am going to continue to try and prevent it in any way I can using what info, research, and hard data I have on hand.
Lastly. What would it hurt to have an oil temp gauge?