Boundry lubrication failure? Cummins ISX camshaft

[Doug Hillary]

Hi,
slammds15 - I can only assume that the lubrication system was cleaned correctly first time around

I have seen this on a number of engines where the hardening was faulty. The fact that the brake lobes were OK gives a clue. is there a history of faulty cams on these motors. Cummins have a history of cam issues

Detroit have from time to time read the cam part numbers in situ to ensure they pick up cams with suspect hardening prior to parts being eaten alive!

Other engine families (unnamed on here) are also experiencing similar cam quality issues

Residual dust can have a long life in any engine if it is not cleaned correctly!

Going by your comments it is not a lubricant issue

 

[slammds15]

It was cleaned as well as I could do it. I blew out the rocker shafts and shot brake parts cleaner through them all. sprayed out the iside of the block when the pan was off and also blew the crank out. Its hard to do the job you want to do and should do when your service advisor is telling you different. The ISX is known for cam failures but not with this milage. I'm thinking the toothpaste like oil when it came in from being dusted played a major part in the failure. I also think there was residual contaminated oil. Also their service intervals are rather extended. I believe they are using Quaker state 15W40 bulk oil.

Either way the owner is happy, we finished his truck off in time to be in the christmas parade

 

[mechtech2]

With only some areas affected, it sure could be faulty materials/machining/finish, or heat treating.

But who knows if the oil was ever run real low?
Or sometime in it's past, started with no oil as an 'OOPS' by a mechanic?

 

[onion]

I left the Cummins dealership in 2000, so I've had very little experience with the ISX engine, though I've worked on more M11, N14, 855, B5.9, and C8.3 engines than I could count... not to mention lots of Deere, Mercedes, and Detroit engines in the years since. So just from general diesel engine experience- none specific to the ISX- I'll throw a few ideas around:

Is there any sign that valves have contacted pistons? Was the camshaft/geartrain timed properly? Makes me suspicious that only the exhaust valves have failed... knowing retarded cam timing will cause only the exhaust valves to contact the pistons.

Was the valve lash set correctly? Probably no way to know for sure, but I do know that excess valve lash can beat the [censored] out of a valvetrain... and wouldn't do that cam lobe any favors.

Are there any recent overspeed codes in the ECM? Any oil pressure codes?

Was the cylinder head replaced last time? Were the counterbores in the block machined? Were the rocker shafts replaced and are they drilled correctly? What I'm getting at here is this: Could there be any obstruction to the oil pressure supply to the cylinder head or just to the exhaust rockers? This oil gallery is often plugged when machine work is done on the engine block to keep metal shavings out... and that plug (usually a piece of foam rubber) could have been left in place (I saw that happen before on an old 855... not pretty). Also I suppose that a new cylinder head or rocker shaft could have been machined incorrectly- I've seen stranger things.

Were the rocker arms replaced during the previous overhaul? Could this be a bad 'run' of parts? Any service bulletins on the matter?

 

[nthach]

So a bad case of dust ingestion caused this?

Also, I've read Cummins is stopping production of the ISM for trucks and buses and instead pushing a smaller version of the ISX. How will a smaller ISX compare to the ISM/M11 in say, a regular 40-foot transit bus using an Allison B400/500 series or Voith D864.3E tranny?

 

[slammds15]

No the rockers were not replaced because there was no sign of wear at 24,000km. no damage to the valves, bridges, or rocker ends. no real sign of excesive valve train clearance. With the crank pinned and the cam wedges in place there is no way to mess up cam timming. Any idot could do it Oil delivery was no an issue, no DTC's were set. Cummins wanted a print out, they are gettin pretty sticky with warranty work lately.

The head was a "new" part and counter bores along with everything else was checked before reasembly.

I was talking to a broker who runs for this company yesterday while working on his truck (I usually hate drivers in the shop but this older fellow was good stuff) he refuses to have his truck serviced at their own shop. Apparently they use some sort of "recycled" oil, cheap oil and fuel filters and washed air filters as well.

Their maintenance practises scare me, but hey it gives me something to do every day

 

[slammds15]

Originally Posted By: mechtech2
With only some areas affected, it sure could be faulty materials/machining/finish, or heat treating.

But who knows if the oil was ever run real low?
Or sometime in it's past, started with no oil as an 'OOPS' by a mechanic?


They have rediculous engine safety parameters set in place to avoid this. No oil pressure means engine stops. Although it does have a timmed session at which point engine damage could occur. But with this detrimental effect damage would occur in other areas much quicker than camshaft lobes.

 

[nthach]

Originally Posted By: slammds15
Originally Posted By: mechtech2
With only some areas affected, it sure could be faulty materials/machining/finish, or heat treating.

But who knows if the oil was ever run real low?
Or sometime in it's past, started with no oil as an 'OOPS' by a mechanic?


They have rediculous engine safety parameters set in place to avoid this. No oil pressure means engine stops. Although it does have a timmed session at which point engine damage could occur. But with this detrimental effect damage would occur in other areas much quicker than camshaft lobes.

Is it theoretically possible to damage a electronically-controlled engine via the STOP ENGINE OVERRIDE swtich during a low oil situation, or the engine shuts down regardless?

 

[onion]

What do the bearings look like?

 

[Colt45ws]

Originally Posted By: nthach
Originally Posted By: slammds15
Originally Posted By: mechtech2
With only some areas affected, it sure could be faulty materials/machining/finish, or heat treating.

But who knows if the oil was ever run real low?
Or sometime in it's past, started with no oil as an 'OOPS' by a mechanic?


They have rediculous engine safety parameters set in place to avoid this. No oil pressure means engine stops. Although it does have a timmed session at which point engine damage could occur. But with this detrimental effect damage would occur in other areas much quicker than camshaft lobes.

Is it theoretically possible to damage a electronically-controlled engine via the STOP ENGINE OVERRIDE swtich during a low oil situation, or the engine shuts down regardless?

When I worked for county shop, they had a dump truck come in with a trashed engine. Drain plug had fallen out and it lost all oil. The driver just kept restarting the engine and driving it until it would shut off again.

 

[TiredTrucker]

I am having a camshaft replaced in my ISX 435 ST for exactly the same problem. The pics at the start of this thread look darn close to what my camshaft looks like. Cummins has had numerous problems with camshafts in the ISX. I have heard of several situations such as ours on cams over 500,000 miles. I read a bulletin put out (a few years ago) how Cummins was improving the metallurgy to address the problem. It does not seem to be lubrication related. My injector cam was pretty good, but the valve cam was trashed along with 3 rollers. I had Allied Oil and Supply branded oil (very similar to Rotella) in it. No indication of anything in oil sample results. Only found when running the overhead. The rest of the internals look pretty good for a 768,000 mile engine.

 

[OVERKILL]

Originally Posted By: TiredTrucker
I am having a camshaft replaced in my ISX 435 ST for exactly the same problem. The pics at the start of this thread look darn close to what my camshaft looks like. Cummins has had numerous problems with camshafts in the ISX. I have heard of several situations such as ours on cams over 500,000 miles. I read a bulletin put out (a few years ago) how Cummins was improving the metallurgy to address the problem. It does not seem to be lubrication related. My injector cam was pretty good, but the valve cam was trashed along with 3 rollers. I had Allied Oil and Supply branded oil (very similar to Rotella) in it. No indication of anything in oil sample results. Only found when running the overhead. The rest of the internals look pretty good for a 768,000 mile engine.


You mean a UOA didn't tell you that you had failing cam lobes? Impossible!

(heavy sarcasm)

This thread never did really reach any sort of conclusion, LOL. Do you have pictures of yours?

 

[TiredTrucker]

Unfortunately, no pictures. It didn't register with me to take any at the time for posting. I was just shocked at the way the cam looked, and hadn't quite planned to spend that much money when I put the truck in the shop for a laundry list of maintenance items. I only had one lobe that looked identical to the picture at the beginning of this thread. The other cam and the bearings on this one looked good. Would have thought I would have heavy scoring on the showing up under bearings, but that wasn't the case. One other owner I talked with a few months back had this same issue. That caused me to look up anything I could find on it, and I happened across a Cummins item that said there was a change to the metallurgy in subsequent cams. Probably one of the engine items being out sourced to China.

Yeah, no indication from UOA's. I have run UOA's on virtually every oil change since I got this truck. It now has 763,000 miles on it. Little fluctuations here and there, but nothing to raise an eyebrow. Heck, even when I dump my used oil into a 55 drum for disposal, I use a funnel with a screen and never have found any filings or such to cause concern. I guess the one thing that I haven't done is hack open used filters.

 

[TiredTrucker]

Update I came across. Cummins issued a tech bulletin on this issue. They are attributing the problem to the rockers and NOT the cam. Seems the rockers were sticking and "slapping" the cam lobes. Do not have the bulletin number. Will try to find. I guess it was a good thing we did all the rockers when we did the cam. Might be a wise move for anyone else who runs across this problem.

 

[vaboom123]

I've seen quite a few ISX cams messed up, but that one got it pretty good. The fleet I worked for had around 20 otr internationals with isx motors in them. They all had to go in for the recall for the cams.

 

[Kestas]

Since the pattern of failure is limited to the higher stressed lobes, it could be a hertzian stress failure. In laymen's terms, this is where the material "gave up" and reached the end of its life. This would show up in cross section during metallographic examination. You would see microstructure decomposition a short distance under the surface where material sees the highest loads. The fact that spalling occurred in the pattern shown, and not just wear, is sometimes a clue.

Hertzian overload isn't for certain, but it can't be ruled out.