One of the more impressive failures I've seen.

Lower idler gear bolts were reused and the bolts sheared off.
Then it was..Everyone out of the pool!

Blew the Air compressor out with a large section of the gear housing.


Compressor gear and whats left of the lower idler, which is under the small cover.



It jumped time and took out the rear bank 4,5 and 6.
Broke all the valve bridges and bent valves, looked like a bomb went off.
No saving that one.

I guess when they have big ass warnings in the manual to not reuse those bolts, they're not kidding.

Some other shop back east was in there a few months ago.
About $40K for a new engine, if one is even available.

Long nose Peterbilt car hauler that's loaded with cars, which needs to be off loaded somehow makes it a bad day all around.

Some people just are stupid. If the manual says put in new bolts then that is what you are supposed to do. I had a guy when I worked on John Deere Construction equipment who reused his head bolts on a 414 and wondered why they snapped and he blew the head gasket. It was a frikking mess and getting the stubs out in the block sucked. He ended up with bent valves, pushrods and flat spots on his rod and crank bearings. It ended costing him a butt load more than if he'd done it right.

Just curious as to why the bolts could not be re-used.

quote:

Originally posted by armored:
Just curious as to why the bolts could not be re-used.

They stretch when torqued initially and lose some of their diameter. Retorquing stretch to yield bolts is a definite no no.

quote:

Originally posted by armored:
Just curious as to why the bolts could not be re-used.

TTY (torque-to-yield) bolts are purposely designed to stretch and snap back to maintain proper tension. While this is somewhat true of any bolt, on TTYs this capability only lasts one use (the initial installation). If you re-use them they will no longer maintain this tension. TTYs are typically tightened to X number of ft.lbs. (or newton-meters or other unit), then to an angle specification.

That ain’t suppose to look that way, right?

What year ISX15 and is it a single or dual cam?

That is indeed an impressive failure. Those warnings are there for a reason. What a mess!

Shoulda answered the phone and bought that extended warranty.

I've dealt with torque-to-yield processes in high volume production of engines and the requisite requirement to replace all bolts if the tightening process rejects. There is no special design for the bolts. We just use very advanced DC servo spindles that can detect the onset of yield and stop right when they reach it. This should result in no significant necking down or loss of diameter.

It gets worse when designers spec high strength bolts like metric 12.9 grade. They can handle more load, but once they go into yield the load curve is rather sharp and they start necking down very quickly leading to failure. A 12.9 taken to yield should not be reused, but a 10.9 or 9.8 taken to yield has a flatter load curve at the peak and may have enough margin to be reused once or twice. This is a big concern when you know the service people in some parts of the world will not replace the bolts as indicated in the service manual to save a little money. Don't ask me about how much damage they cause when they reuse high pressure fuel lines that have a "crush to seal" endform and should be replaced every time they are removed.

If I am involved I tell the designers to stay in the elastic region of the bolt to avoid reuse issues in service. However, sometimes a torque + angle or clamp load spec is given that gets very close to yield in practice, even though TTY is not specified. Variation in the bolts can result in some starting to yield while others do not. Usually this happens after the product is designed and they find in development or service that they need more load to keep things together.

More problems happen because there is no way to measure the onset of yield or clamp load during service events. So the service engineering people try to approximate the production line specs with manual torque + angle specs, but the process is not even close to the precision we get with production equipment. In production, I can fine tune the torque and angle to anything I want, using multiple progressive steps along with various advanced functions. Service is invariably 60, 90, 120, 180 degrees on the angle step because that is what is easy to perform manually. And if the tech is 10 degrees off, you can be under or over tolerance on clam load depending on the direction.

But if the manual says to replace the damn bolts when you replace the part, then you had better do it.

quote:

Originally posted by Lefty Sig:
What year ISX15 and is it a single or dual cam?

2013, 2250 series, 1st gen common rail, no injector cam.
The gear that failed drives the HP fuel pump.


Got the front bank too.


When it let go it was sudden but it was a work in progress and had to have been making a hell of a racket before it gave up.

The gear train is noisy enough as it is, if it's off there is no mistaking that something is not right and it will shit the gears.

That's the easier version to set up as that lower idler is non adjustable.
The other one can be a PITA to come out right.

quote:

Shoulda answered the phone and bought that extended warranty.

I'm gonna have to steal that, too funny.

The guy is buying a new 7/8 engine to get going and will take it up with the other shop about buying an engine.
About a $50K bill at the moment.

Not all torque angle bolts are one time use.
Some, like a Volvo rocker shaft is 5 times.
Multiple steps with a final 20 ftlbs + 120 deg. New bolts are around 70 ftlbs at 120 deg with a gradual increase.

Ones that haven't been marked and been re-used to many times will get to about 25 ftlbs then go soft and be around 18 ftlbs or so at 120 deg.

Some things you can use an impact to rotate the bolt and quite a lot use that method for everything.
Bad idea on reusable bolts as you won't be able to tell that it has gone beyond use.

You have to take bolt stretch into account when setting valves and such.
Take the ISX. With a feeler blade inserted tighten the set screw to 5 inlbs and torque the jam nut to spec and it's a perfect fit.
Repeatable and consistent.
Adjusting to fit then tightening the jam nut will be too loose.

The last engine I built for myself I used ARP rod hardware and a stretch gauge for torquing the rod caps, IIRC it was .006" stretch or about 35 ftlbs.

All TTY bolts I know of are one-time use only. This is different than torque angle bolts.

The rig wound up back on the hook and headed back to the Dealership that botched the job.
They tried to claim warranty but after the Cummins rep looked it over and found it to be workmanship it looks like they are footing the bill for it and can battle it out there.

This was pretty ugly, fairly new truck.

Did't have to fight warranty for that one, had a complete engine in about a week.

Would that be considered an exploded view?

quote:

Originally posted by powermad:
This was pretty ugly, fairly new truck.
Did't have to fight warranty for that one, had a complete engine in about a week.

Looks like an oxymoron installed the piston on the wrong side. The out side.