Cummins Isx 600 cm 871 broken exhaust valve #6 cylinder

[Mile Marker 42]

Nice read. I believe lugging is a serious issue no matter what engine you have. Most people who lug their engines don't even know they are doing so outside of maybe the temp gauge is rising too much and they realize they have an overheat issue.

[vito.a]

It's almost impossible to "lug" an engine with 1850 ft lbs of torque at 1200rpm connected to an Allison six speed transmission that is programmed for this exact engine.

These failures are well documented. They are caused by "chordal valve failure". This is caused by the EGR system recirculating acid back into the engine and settling onto the back side of the valve. The resulting corrosion then eats away enough of the valve head until it cracks and a piece breaks off. This broken piece then damages the piston, cylinder liner, and the turbo.

There are two ways to prevent it. Replace the valves with high quality Inconel stainless steel and compatible seats. Or address the EGR system and prevent the acid from entering the engine.

[Wild Card]

Originally Posted by vito.a

It's almost impossible to "lug" an engine with 1850 ft lbs of torque at 1200rpm connected to an Allison six speed transmission that is programmed for this exact engine.
.

Wrong

[Smitty77]

Originally Posted by Smitty77

ISX600 CM870 EGR only engine in our 07 coach. They do not seem to have as many issues as the ISX600 CM871's with EGR and DPF. Here are some random info sharing from my memory (Stress from my memory, as it was over the last two years or so, while researching for a new coach. And, certainly my memory could be off!):
> The CM870 and CM871's share a common head, with the same alloy used for the valves
> The failure of #6 (And also #5) valves are seemingly caused by 'gunk' building up in the EGR and allowing an acidic flow from this gunk down into these two valve positions
> The configuration of the CM871 adding DPF along with the EGR, cause a slight increase in the angle of the the EGR towards those cylinder positions
> Gunk seems to be more prevalent in engines not run for longer periods of time, and also engines that might sit for long periods of times. Areas with higher humidity might also contribute gunk build up within the ERG Tube. (So. Over the Road Truckers who have these engines running for many more hours and thousands of miles then an RV would see in duty - do not seem to build up the 'gunk' as fast. Often going to the 250K range before EGR's need serious attention. Whereas an RV'er might put on a few thousand miles at a time during a trip. And from a article I read years ago in I think an FMCA magazine - commonly 4-5 hours is the 'average' time driven per day for RV'er's. (Sure, some go the 8, 9 to 10+ hour days as needed. And others travel about 2 hours - for sure it varies... But some how this article came up with the 4-5 hours average per day for RV'er's.). And then after a trip, these RV's might sit in storage for weeks or months at a time. Allowing the slow seepage of the 'gunk' into these two primary cylinder head with common valve problems.
> The ISX in most RV applications, have relatively low running RPM's in 6th gear while running down the interstate. The rear axles of some units, I've been told some Monaco's could be option out with different gearing that would spin the engine at a higher RPM. But the bulk, use that combo of HP/Torque and just ease on down the highway.
> Some RV owner's are 'Get in and drive!' - letting the ECM's between the Cummins and Allison 4000 just handle it, handle it, handle it! And as mentioned in the earlier post, the Economy mode will change the shifting pattern, reducing RPM's being run a bit lower.
> Some sites I've read, with Over The Road Fleet owners running many, many trucks with ISX's - suggest that at least once each day they ask their owner's to drop it down a gear if needed, to run for a good 30 mins or so at 1750 or so RPM. They reported seeing less problems on EGR build up, and DPF's had less problems and too. They speculated that the higher RPM's, and hotter exhaust, allowed the EGR's to help blow them selves out a bit of soot and thus reduce gunk build up.
> The CM870's EGR only, seemed to benefit the most from the higher RPM running mentioned in the above. And speculation it was due to the less back pressure of having no DPF to run thru, allowing a higher pressure and heat to flow more back thru into the engine for repeated burning. (AND WHAT A GREAT IDEA THAT WAS... DUMPING HOT EXHAUST BACK INTO AN ENGIE - NOT! A real shame regulators did not stress MPG improvements, over gasses in the exhaust released. As then it could have been a win/win. Higher MPG, less gallons burned, and thus also less exhaust gasses released... Now, poorly designed and forced in by regulatory parties who had no real clue. They burn more fuel, greatly reducing the gains of the reduced exhaust gasses from the regulations. Toss in the reality that the CM870 EGR and CM871 EGR/DPF engines, ALL, seemingly have a higher probability of the Smog Stuff not working efficiently - and even lower MPG, and thus even higher exhaust gasses... as a result. (Semi rant off.).

Me? And my relatively young at 49K ISX600 at time of purchase. What I do:
> I do add either Optilube Summer Blend and or Power Services Diesel Klein(SP?) in each tank. Minor cost in the scheme of things, and it adds some Cetane and helps keep injectors optimized too. Figure the higher Cetane may result in a bit more efficient burning the fuel, so less unburnt fuel being cycled into the EGR.
> I avoid idling as much as possible
> I commonly drop to 5th gear, to keep the RPM's up a tad, as well as to also reduce lugging (Depends upon the Speed Limit, and highway being driven. Light rolling hill conditions, for sure 5th gear if traveling 65MPH or under.)
> Never use Economy mode
> And towards the end of a days drive, the last 20-30 mins or so, drop gears to get the RPM's to float between 1650-1750 or so. Then of course do a normal cool down period before stopping. Usually accomplished from pulling off of an interstate or highway, and onto surface streets for at least 5 mins or so.
> When climbing grades. Even though the gobs of Torque/HP don't really need me to do so. I'll drop gears and run from 1750-1900 or so up the grade.
> I choose to not optimize potential MPG, over trying to optimize keeping the EGR from clogging up earlier with soot/gunk
> And, at 75K (Now at 60K) I will have an EGR Tune Up accomplished. Clean the EGR Tube (And really look forward to seeing the condition of build up at that low of miles.), MAP and other Sensor replacements, clean maintain (replace if needed) the Flapper door... (I'll do this to get a good understanding of how this engine is doing from the EGR perspective... And MAP sensor getting dirty is one of the highest reports of problems with EGR's not running efficiently. And an EGR, again already a bad idea for diesel, not running efficiently - will lower MPG and have a higher probability of soot/gunk build up

(Those above, are just my choices and how I've started to run our ISX. Certainly am not an expert, and have not doubt many experts will say none of these things are needed. But, my engine. My coach. My money... So, I'll do so for awhile and see how things go!)

I'll also share that I believe the ISX600 CM870's is a good engine overall, for that level of smog era... I believe the ISX600 (And 650 too.), are also good engines. They will need a bit more preventative maintenance then the CM870, as they do have both an EGR and DPF. And if I were the owner of, and or had bought one myself, a CM871 engine. I would pro-actively work into the budget the replacement head with new improved inconel alloy valve train...

Best to all,
Smitty

I wanted to add that I often do things differently then others. I like to try different techniques while learning a new to us rig. My experimenting with higher RPM's, sacrificing ultimate fuel economy while doing so, is because of my desire to keep what I consider the weak link in the ISX CM870 engines - the EGR - as healthy as possible. And the hypothesis of hight RPM's yielding higher and hotter exhaust gas flow, 'possibly' helping clean out the EGR tube from sludge/gook build up - is my reason for trying this.

However the ISX, and remember when researching on the all knowing Internet, the ISX comes in many configurations, and have ECM's flashed to many variables of HP/Torque as well as HP/Torque 'curves'. So reading info, needs to be somewhat factored as to 'What engine, and in what usage?' (Fire Trucks, Over The Road Truckers and RV's may all have an ISX in them - but many variable between them...).

I had meant to include in my 'Crisp' (NOT!) earlier post, this other comment from a Trucking Industry post (Where MPG and Fleet Fuel Economy, is king!). It's in regards to the abundance of Torque that these ISX's produce, down to low RPM's too... Here is a snippet:

"When you are going up a hill and feel the urge to downshift – wait. The engine can drop as low as 1000 RPM without lugging;"

In this article, they're talking about multiple gear Over The Road Truckers, with 430HP being a common ISX trim. And they do talk about the 1250-1650 relatively broad/flat higher end of the ISX's Torque Curve capability.

I share this now, because many with ISX's not concerned about EGR (And perhaps DPF too. But I have zero DPF experience first hand...)... The target RPM to probably stay under would be the 1650, say + or - 50RPM's.

I personally, am not sure that this one paper, again geared towards OTR Driver Education on learning the ISX's capabilities - was for MPG... is accurate in the comment in the quote about not 'lugging' down to 1000 RPM. (It's contrary to many other Forums and Articles I've read, where many OTR Fleet Owner's and Fleet Maintenance Manager's have voiced concerns about the impact of lugging the ISX, and potential damage to sleeves.

One other consistent thread in all of the items I've read, was the 'Don't idle the ISX for longer then needed!'. (Needed to cool down some after a run, and or to let Oil Pressures stabilize. Almost always, the 'Once the idle smooths out a bit, go ahead and get going.'... (I personally, leave Jake Brake Off, and keep my foot out of the pedal until temperatures have creeped up, and oil pressure has dropped down a bit (Indicating the oil is also warming up.).

====

Just wanted to add that snippet about RPM ranges on our ISX's. And always recommend contacting Cummins Technical Support and asking them for the info on your specific Serial Number of your ISX - as HP/Torque Curves change over the years, and from one CM build to another!

The article I have saved as a PDF was not readily available to share a link. But for more fun reading, look up 'Progressive Shift ISX' or 'Progressive Shifting ISX'. Most of the hits will be either discussions on forums, or papers from different view points... All, is just more info to sift thru...

===

As I've read some more recent posts and articles, I think I will pull back my 30mins runs at 1750RPM, to 10Mins, and then target 1650RPM for another 20Mins or so... While fuel consumption is not my main goal in this unofficial EGR health attempt testing, nothing wrong with saving some fuel too...

And to each their own... Part of the fun of this RV'ing thing, is the learning and info sharing amongst us all... And as Dennis Miller used to say often 'I could be wrong...' - certainly are words I use too often!

Best to all,
Smitty

[Jarlaxle]

1650RPM for a 15 litre engine is screaming. I drive one, and unless I'm pulling a 40,000+lb load, I will probably never hit that. It usually shifts around 1600RPM (10-speed Autoshift) and will pull down below 1100 before kicking down on a long grade. This engine sees MUCK more weight than any RV. (I scaled at 77,900 a couple weeks ago.)

The engine is unrebuilt and has the original turbocharger with 580,000 miles and ~30,000 hours. IIRC, it's 500HP.

[Smitty77]

Originally Posted by Jarlaxle

1650RPM for a 15 litre engine is screaming. I drive one, and unless I'm pulling a 40,000+lb load, I will probably never hit that. It usually shifts around 1600RPM (10-speed Autoshift) and will pull down below 1100 before kicking down on a long grade. This engine sees MUCK more weight than any RV. (I scaled at 77,900 a couple weeks ago.)

The engine is unrebuilt and has the original turbocharger with 580,000 miles and ~30,000 hours. IIRC, it's 500HP.

Cool having the 10-Speed Autoshift!!! And 580K on OEM engine and Turbo is nice to read.

What CM Config is your ISX500?

TIA,
Smitty

[KFed 90-10]

Ive got a 2013 ISX in the 525 hp, single cam configuration. Ive had this rig for 2 years now and was initially freeked out over all the issues describered here in. Bases on my research, my engine doesnt suffer from these issues, at least not as often. Ive got the 13 speed Eaton Auto Shift with the paddle shifter. At full throttle, it shifts at 1800 rpms and doesnt hit 13th gear until 65 mph. I often manually down shift when climbing hills. If I maintain at least 1300 rpms, not many hills will slow me down. The 13 speed allows me to always be in the rpm sweet spot. My mechanic, a former Freightliner shop foreman told me yes you can lug these engines. He told me to drive it like I stole it and the engine will run cleaner with less exhaust filter build up. So, thats what I do, usually averaging between 6.5 and 7.5 mpgs.

[Smitty77]

Originally Posted by KFed 90-10

Ive got a 2013 ISX in the 525 hp, single cam configuration. Ive had this rig for 2 years now and was initially freeked out over all the issues describered here in. Bases on my research, my engine doesnt suffer from these issues, at least not as often. Ive got the 13 speed Eaton Auto Shift with the paddle shifter. At full throttle, it shifts at 1800 rpms and doesnt hit 13th gear until 65 mph. I often manually down shift when climbing hills. If I maintain at least 1300 rpms, not many hills will slow me down. The 13 speed allows me to always be in the rpm sweet spot. My mechanic, a former Freightliner shop foreman told me yes you can lug these engines. He told me to drive it like I stole it and the engine will run cleaner with less exhaust filter build up. So, thats what I do, usually averaging between 6.5 and 7.5 mpgs.

Cool info sharing - thanks! Really like the 'drive it like you stole it'! And also liked that another mechanic gives the input that lugging is possible, and higher RPM's can keep the EGR (With DPF in your case. Suspect CM2250 or maybe CM2350(?) from memory.)

I think the Allison 4K is a good trans! And the six speeds coupled with the HP/Torque of an ISX does get the job done. Compared to OTR weights, I suspect I'd be considered a mid weight(?) - as we our little CRV, and each fully loaded, we're at 53K pounds (Sometimes creeping up to 53.5K - when the wine/scotch/bourbon/rye is fully stocked after Costco visits!). The fewer gears available, means when traveling at highway speeds, we have 5th with not too high, but obviously higher, then 6th gears RPM's would be. Dropping to 4th, I've never been slowed on a grade, and the RPM's are up high enough to be closer to peak HP, then peak Torque...

Really enjoy the info sharing on this thread (Heck, on all threads in IRV2!).

Best to all,
Smitty

[RonAz]

Long hills can be your friend. Today's vehicles have so much power that they do not work very hard on the flats. Pulling long hills at close to full power helps to burn off the deposits in your engine and does a "natural" regen of your DPF. I was running a 425hp for years at 101,000 GVW.
After a long pull I always found the engine to idle smoother and to just run smoother. By long I mean 20-30 minutes minimum pulling hard. I usually pulled the steep passes at 35mph which provided the time for the engine to clean itself out.

[Smitty77]

Just had a friend with a Monaco Signature, think it's either a 2006 or 2007, but definitely has the CM870 config ISX600 - had an EGR related fault code, as well as the engine was not performing as usual.

Believe he's in the mid 80's K range now.

I sent him the link on the Rawze's 'EGR Tune-Up', so he had done some good diving into forums and YouTube on EGR's in general.

He struck out a Rush's (Made an appointment at the one up in Miramar in San Diego.), as when he showed up they basically did not want to get involved with a Motorhome... So then he bumped over to Cummins of El Cajon. Worked in advance with the Service Manager, and per the codes, he felt pretty confident it was an 'EGR Motor' (The words that were shared with me... I assume he meant the control of the flapper valve(?).). So they pre-ordered those parts, for his future appointment.

Last week they worked on the coach (Wrong side of the engine at first, thinking it was a CM871...), and installed the new 'EGR Motor' (Had to wait to get some other related parts, so another day in the shop.). He said the Service Manager did not feel any of the sensors should be replaced, or serviced... So no 'EGR Tune-Up, and I frankly was not clear on if they cleaned the tube out while things were apart or not...

But he's out, and the first drive no error codes, and the engine ran as it used to run - so he's a happy camper!!

I share this, as the Service Manager said that the 'EGR only ISX's were much less problematic, and simpler, to work on.' (Wording to that effect.) And also because after these years of ownership - it was the EGR that caused him problem...

So good 'Hmmmmm' info!

Best to all,
Smitty

[Jarlaxle]

Originally Posted by Smitty77

Cool having the 10-Speed Autoshift!!! And 580K on OEM engine and Turbo is nice to read.

What CM Config is your ISX500?

TIA,
Smitty

Actually, it's horrible. The autoshift flunked driver's ed...in honor of how it shifts, I call it Lurch. It's impossible to start moving smoothly, it makes all sorts of weird noises, and the driver has very little control over it.

I have no idea what CM the engine is.

[KFed 90-10]

Jarlaxle, that's unfortunate that your 10 speed auto shift is horrible. My 13 speed Eaton is smooth as butter. Either in automatic mode or manual. As most know, the trans doesn't actually shift through all 13 gears. It starts out in 2nd and skips its way to 13 pretty quickly. About the only time I need to utilize the paddle shifter is when climbing steeper, longer hills, as the trans doesn't down shift until I drop below 55 mph and out of the rpm sweet spot. So a quick tap of the paddle shifter solves this problem. I wanted to get the word out regarding my experience with the Eaton, which I absolutely love, and couldn't imagine only having a 6 speed trans.

[Jarlaxle]

Originally Posted by KFed 90-10

Jarlaxle, that's unfortunate that your 10 speed auto shift is horrible. My 13 speed Eaton is smooth as butter. Either in automatic mode or manual. As most know, the trans doesn't actually shift through all 13 gears. It starts out in 2nd and skips its way to 13 pretty quickly. About the only time I need to utilize the paddle shifter is when climbing steeper, longer hills, as the trans doesn't down shift until I drop below 55 mph and out of the rpm sweet spot. So a quick tap of the paddle shifter solves this problem. I wanted to get the word out regarding my experience with the Eaton, which I absolutely love, and couldn't imagine only having a 6 speed trans.

Every Eaton we have had (at least six, all 10-speeds) is horrible. They start in second but won't skip-shift. The DT12 is excellent except for liking to shift halfway up a long grade...the Volvo 12 is smooth enough but lugs the engine horribly, and the driver has zero control over it.

[pbensen]

Originally Posted by Rpurcell

My engine broke about 30% of the exhaust valve off , found the piece in the vgt, had the coach brought to my shop in Florida. We will repair it.

How did the repair go on you ISX? Did Cummins help you out on it? What all did they have to replace? If you don't mind saying; How much did the bill come to?