Cummins ISX broken valve in #6

[08Navigator]

Originally Posted by Ivylog

The Powerstroke additional lines remove hot water from the back of the heads, not cold in.

I did look at a ISX in a truck today...looks identical to my 08 Navigator and much easier to get a picture:l. OK, mine do not have the elbows.

Wow!! After viewing this picture....I guess my theory of why the liners scored etc is out the window...appears the OTR trucks use the same concept of amount of flow out of the head in the rear...and they don't have the premature failures... SO I STAND CORRECTED
However, I am leaving mine modified, as for when checked with a IR reader..I dropped the back corner of the head approx 15 degrees when climbing a hill..BUT pictures don't lie, my theory of why #6 fails on the RV's premature being linked to the output hoses.. is WRONG!

[08Navigator]

Originally Posted by srh

I, too, want to add my appreciation for the great discovery that would save people thousands of dollars and the agony. More appreciated the fact is that you have taken the time to share it in a public forum as such. I'm not as mechanically talented as many other folks who have actively participated in a meaningful way on this discussion. But let me say that your solution is making sense and it can even be done by novices like myself.

If you don't mind me, I have a couple of questions that you or perhaps others, more knowledgeable than me, could shed some light on:

1. If the two heater hoses on the engine block are the causes of the problem, then I would take it that the problems occurred, perhaps during the winter months when the two lines were open, Correct? Perhaps this maybe the reason why all the ISX's of that era have not failed. I had an 08 600 HP ISX that I sold and had over 60K miles on it with no issues. And there are many more like that.

2. Curious minds would like to know if any of these ISX's have failed during the summer months?

3. Lastly, I'm wondering why the Cummins engineers did not see this obvious design flaw? To that end, are all new ISX's made with the same design?

Thanks, again!

Hi, coolant flows through both hoses non stop , in a loop right back to the water pump. The Thermostat does not have to be open, the moment the engine fires what starts flowing...that's the reason you get heat out of the vents prior to the engine being hot and the thermostat opening. So, ambient air temp has no effect at all.
At my hearing with Cummins..I did ask them your #3 question, and they informed me that any accessory attached to their engine would need to be approved by engineering....I just ASSUMED that since aqua hot was an accessory used by the small RV industry, Cummins never did any dyno testing to look for hot spots...
Now I am as baffled as to why only RV's as the rest of the world...the mystery continues...I do know the valves rusted and I do know it takes heat to make steel crack in that fashion...going back to drawing board!

[Ivylog]

I’m sorry but I am not buying into 08 Nav’s solution. The restrictions in the water is to force more water around the hottest cylinders...3 & 4 in the middle of the engine. Those cylinders do not have restrictions in the castings...1/2 & 5/6 do. The majority of the cooling is done around the cylinders, not in the head. Cummins increases the water flow around 3/4 for more cooling...so much for faster moving water not able to cool as well. If anything the extra water flow provided by the two lines increases the cooling because I stayed at a Holiday Inn recently.

In the pictures of the broken #6 valves (before they have broken completely off or rusted off) there are pieces around the perimeter broken off. This did not happen because of heat (especially on a intake valve) it’s the result of the piston hitting the valve. This gets me back to a problem with the Jake not releasing #6 soon enough. I may reduce the amount I use my Jake.

Is restricting the water flow with a T going to hurt anything, probably not but I doubt it’s going to solve this problem. I do wish it would be that simple and that Cummins didn’t know what they were doing.

08 Nav, I do appreciate all you’ve done from rebuilding your engine to the 5” exhaust but I do not agree with you on the amount of water flow being the problem.

08 Nav, I see we were both typing at the same time...glad you will not take any offense to what I’ve posted above...I had my doubts before looking at a truck. I may still go and look at the ISL in my previous Dynasty for where the water comes off the head for the heater and Ahot.

[08Navigator]

Originally Posted by Ivylog

I’m sorry but I am not buying into 08 Nav’s solution. The restrictions in the water is to force more water around the hottest cylinders...3 & 4 in the middle of the engine. Those cylinders do not have restrictions in the castings...1/2 & 5/6 do. The majority of the cooling is done around the cylinders, not in the head. Cummins increases the water flow around 3/4 for more cooling...so much for faster moving water not able to cool as well. If anything the extra water flow provided by the two lines increases the cooling because I stayed at a Holiday Inn recently.

In the pictures of the broken #6 valves (before they have broken completely off or rusted off) there are pieces around the perimeter broken off. This did not happen because of heat (especially on a intake valve) it’s the result of the piston hitting the valve. This gets me back to a problem with the Jake not releasing #6 soon enough. I may reduce the amount I use my Jake.

Is restricting the water flow with a T going to hurt anything, probably not but I doubt it’s going to solve this problem. I do wish it would be that simple and that Cummins didn’t know what they were doing.

08 Nav, I do appreciate all you’ve done from rebuilding your engine to the 5” exhaust but I do not agree with you on the amount of water flow being the problem.

08 Nav, I see we were both typing at the same time...glad you will not take any offense to what I’ve posted above.

I agree 100%..I stand corrected..I really thought it was the heat , best intentions, honestly. I hope I haven't caused anyone any work! I told ya I am not a mechanic!!

I do have a question...My engine had the same size coolant holes all the way down both sides of the block...you are saying you have seen them with different size holes in the rear?

I think the rust pits start the cracks, and the heat finishes the job..It could be as simple as the seats and valve angles get so pitted that the heat can not be transferred properly.. BUT that still doesn't explain why RV's?
Couple thoughts tho...I think if something went wrong with the engine brake, it wouldn't effect intake valves, nothing ever hit my pistons...The scoring of the liners is surely heat...maybe the motor is lean back there...but again why just motorhomes and #6?

Absolutely no offense taking...I am thrilled that you point out the fault in my theory before others took time to make changes...I really would like to solve the mystery...I am going to keep thinking....the answer is out there!!

[Chief Alen]

I do not have intimate knowledge concerning the isx .

However this very problem was inherent to old style ford 351 engines.

A little background ... my dad loved fords.

He should have fell in love with chevy's 350's as i did, used in boats and autos.

Out of warranty the problem solving fell on me.

The oil galleys in the 351 engines were cast small and the turns always had to be widened .

Just asking the experts here, could the cooling problem not be coolant but oil not carrying away the heat ?

Just asking .

[Mark D]

Originally Posted by 08Navigator

I agree 100%..I stand corrected..I really thought it was the heat , best intentions, honestly. I hope I haven't caused anyone any work! I told ya I am not a mechanic!!

I do have a question...My engine had the same size coolant holes all the way down both sides of the block...you are saying you have seen them with different size holes in the rear?

I think the rust pits start the cracks, and the heat finishes the job..It could be as simple as the seats and valve angles get so pitted that the heat can not be transferred properly.. BUT that still doesn't explain why RV's?
Couple thoughts tho...I think if something went wrong with the engine brake, it wouldn't effect intake valves, nothing ever hit my pistons...The scoring of the liners is surely heat...maybe the motor is lean back there...but again why just motorhomes and #6?

Absolutely no offense taking...I am thrilled that you point out the fault in my theory before others took time to make changes...I really would like to solve the mystery...I am going to keep thinking....the answer is out there!!

08 Navigator I 100% agree with you on the water. Flowing to fast or too slow will impact cooling so slowing it down may help. I think back years when people would pull out a thermostat to keep the water cooler, the water is cooler but the important parts are hotter.

Geek comments now, the only difference between between aerodynamics and hydrodynamics is the viscosity of the water. To invision what the water will do think of air passing over the same surface.

As far as the valve failure it's a chordal failure, I dont agree with the Jake break oppinion. The TSB failure has been on the intake valve and an engine break only works with the exhaust valve. If the actuater solenoid was defective then the valve would fail again the first time the engine break was used. Cylinder 6 only works when it's on full.

If you find the full TSB, I have it they found that the issue was caused by acid eating away at the valve. Based on ISX mechanics comments #6 does run hotter due to being the furthest from the EGR cooler. I think back to when my company was producing a specialty fastener used in offshore well drilling. The initial design called for a zinc dichromate plate over a heat treated part. My competitor's part had an issue cracking in a way no one would expect. The issue is that plate applied in an acid bath and on hardened parts the acid will eat away at it. What needs to be done is to bake the part soon after plate, this is done at 160 deg F if I recall and the acid is baked off. It adds $.05 per pound to the cost but its necessary. So I started to bake them adjusted the hardness just slightly and sold them cheaper at first then after I proved the durability raised the price. At one point I was 25% more than the other supplier but I had 90% of all the volume.

So I do think back to acid, maybe valve was hardened improperly, maybe its coated. Think of all the acid in diesel exhaust and how it gets recirculated. My wife's grandmother use to say if the Queen had balls she'd be the King so who knows. I do think Cummins has data on the failure so fingers crossed it was fixed.

I believe you used valves made from Inconel? I would think the updated Cummins valves would use an Inconel grade, it's not just the acid resistance it needs stress corrosion cracking resistance. So I think you may be pretty safe when it comes to acid.

The scores in the cylinder, was it just #6 and if so was the injector damaged? I was told by Cummins that the debris damaged the injector and diesel washes down the oil and that damages the liner. This sounds reasonable but I cant say either way.

I think it was great you showed the working and steps. Technically it's an easy process, physically it's hard, the head is 400# +/- so that makes most handy DIY people out.

Great job!

[mackwrench]

Just random thoughts, but the truck chassis don't have 20/30' or more of 3/4" hose snaking it's way though the chassis. The coolant in the truck is quickly returned to radiator.
The heater core in the truck also acts as a thermostat bypass to allow a certain amount of coolant to circulate before the t-stat opens. The EGR cooler helped with pre thermostat open coolant flow as well.
It could be the volume of coolant alone that's the problem. Plus the engine water pump is tasked to pump coolant though out the length of the coach and back.


08navigatior, what are your thoughts on adding a "T" in your revised fitting to run a hose directly to the water pump inlet? (heater return)
Perhaps this would help return more coolant to engine with less pump effort?
Maybe it's OEM setup was allowing more localized overheat since most coolant was exiting to the heater hoses..

Or better yet is there any other way to plumb the heaters? Then just have one hose from rear of head to water pump...

Again just random thoughts.....
Rest of my $.02 is dumping the EGR, cooler, related plumbing etc...will probably solve the issue.

Last question, do you have to bleed the air from the system?

Thanks
Todd

[08Navigator]

Originally Posted by mackwrench

Just random thoughts, but the truck chassis don't have 20/30' or more of 3/4" hose snaking it's way though the chassis. The coolant in the truck is quickly returned to radiator.
The heater core in the truck also acts as a thermostat bypass to allow a certain amount of coolant to circulate before the t-stat opens. The EGR cooler helped with pre thermostat open coolant flow as well.
It could be the volume of coolant alone that's the problem. Plus the engine water pump is tasked to pump coolant though out the length of the coach and back.


08navigatior, what are your thoughts on adding a "T" in your revised fitting to run a hose directly to the water pump inlet? (heater return)
Perhaps this would help return more coolant to engine with less pump effort?
Maybe it's OEM setup was allowing more localized overheat since most coolant was exiting to the heater hoses..

Or better yet is there any other way to plumb the heaters? Then just have one hose from rear of head to water pump...

Again just random thoughts.....
Rest of my $.02 is dumping the EGR, cooler, related plumbing etc...will probably solve the issue.

Last question, do you have to bleed the air from the system?

Thanks
Todd

Todd, I don't know...I am not sold on the coolant issue anymore... and without major changes, kinda stuck with the pre thermostat flow design, so dash heat come on at all times....and the Aqua hot "engine preheat" feature still works....I do agree 100% with your final thoughts....dump the root of the issue and your troubles will be gone...still really bugs me...why the RV's??!!
No, bleeding required on my coach, There is a reservoir tank that is far above the Radiator and engine, small 5/16 hoses from tank bottom to top of rad and another to top of thermostat housing...just fill her up and it burps itself..

[08Navigator]

Originally Posted by Chief Alen

I do not have intimate knowledge concerning the isx .

However this very problem was inherent to old style ford 351 engines.

A little background ... my dad loved fords.

He should have fell in love with chevy's 350's as i did, used in boats and autos.

Out of warranty the problem solving fell on me.

The oil galleys in the 351 engines were cast small and the turns always had to be widened .

Just asking the experts here, could the cooling problem not be coolant but oil not carrying away the heat ?

Just asking .

Great thought!....I am far from an expert...but my thoughts on the oil are: Same system on trucks...so the trucks and rv's should have the same lifespan....I did look at the oiling system...and in my opinion pretty much overkill ...they weren't worried about oil hurting HP....they had it flying everywhere, nice size squirters on the bores...enough oil on the rockers ( I know this cause I cranked the starter til I saw oil on the top end prior to firing it up) During tear down, I was a little concerned that the oil system was weak cause the entire top end was feed by 2 each end of block 3/8" holes...but after seeing it flow...no worries there.

[mackwrench]

Originally Posted by 08Navigator

Todd, I don't know...I am not sold on the coolant issue anymore... and without major changes, kinda stuck with the pre thermostat flow design, so dash heat come on at all times....and the Aqua hot "engine preheat" feature still works....I do agree 100% with your final thoughts....dump the root of the issue and your troubles will be gone...still really bugs me...why the RV's??!!
No, bleeding required on my coach, There is a reservoir tank that is far above the Radiator and engine, small 5/16 hoses from tank bottom to top of rad and another to top of thermostat housing...just fill her up and it burps itself..

"Why the RV"?.....
1st thing comes mind is truck ain't got aqua-hot.
I'm not familiar with the aqua hot, does it use a pump to circulate coolant?

I'm wondering if the flow of water, path of least resistance, if the engine cooling system is suffering from lots of coolant flow from those hoses.

I know all diesel Pusher have similar dash heater hose configuration, but this application is big HP, higher engine operating temps and aqua hot.

I'm still thinking your onto something with the cooling system.

More than likely Cummins has a body builder manual that details external cooling system connections

Hopefully the emission delete, the hose fitting redo and quality valvetrain parts you used will be the winning combination.

....but these are just a few wag's.... ha-ha
You boys ever do get to Florida, I'm just a few hours east of Destin... I'll have a beverage with y'all

[Randyman1]

My take on all this is that the most failures were on engines with the potato (dpf) in the exhaust system. More back pressure added with the EGR returning the scooted exhaust and you have more plugging taking place in the filter which creates more back pressure and heat. The difference between trucks and RV’s would be the amount of use (miles) and with the difference in gearing and the ability to keep from lugging the engine as much. Trucks are pulling a load and run long and hard enough each day to keep them running a little cleaner if that term can be used with a DPF system. That’s why there are still some failures but usually at higher miles in the semi’s applications. RV’s are typically driven at a slower pace and maybe run 300 miles on a given day and Grandpa n Grandma 🙂 don’t run them down the road pulling as hard, thus lugging and sooting up the system more. My coach is a pre DPF ISX and based on what I had learned on here a couple years ago I installed the Ugly Fix to keep the EGR and the reburn of exhaust from occurring while cruising down the road. My engine has more power and although the oil is always dark, I think it now stays more of a charcoal color like when it is fresh instead of just turning to black tar. Twice, before I retired, I drove the coach for 18 hours straight to make it home to beat winter storms. I really felt like it did the coach good to run that long because that is more like what that engine was designed to do in a truck application. I have an automotive and mechanical background and really try to pay attention to how the coach is running at all times. We just turned 56,000 miles and it doesn’t use any oil between annual changes and runs like a champ. Just wanted to share my viewpoint on why more failures in RV applications versus over the road trucks. Randy

[mackwrench]

Randy, your dead on. I totally agree the engine's need to be ran hard.
I see this daily on long haul highway vs regional around town units.
A local adult beverage disturbing company I'm familiar with is have a lot of Regen, plugged differential sensor and DPF issues from all day stop and go driving.
Unfortunately removing any emission system components is no good on these trucks.

[Electra 225]

Randy and "mackwrench", I will concur with your statements about load time on the engine. Another case in point would be the large farm tractors like Case-IH who, uses the Cummins engines in their machines, up and over the 600hp size.
I have run these machines, they run wide open at approximately 2200 to 2500 rpm range for hours on end pulling large implements. You only slow the engine to turn around in the field, otherwise it's full throttle for maximum performance. I've personally not heard of the issue RV applications suffer in these machines.

Edit; forgot to mention, of course these tractor engines don't have DEF and all those components to factor in.

[mackwrench]

Originally Posted by Electra 225

Randy and "mackwrench", I will concur with your statements about load time on the engine. Another case in point would be the large farm tractors like Case-IH who, uses the Cummins engines in their machines, up and over the 600hp size.
I have run these machines, they run wide open at approximately 2200 to 2500 rpm range for hours on end pulling large implements. You only slow the engine to turn around in the field, otherwise it's full throttle for maximum performance. I've personally not heard of the issue RV applications suffer in these machines.

Edit; forgot to mention, of course these tractor engines don't have DEF and all those components to factor in.

not to jack this thread but...Your farm equipment must be a few years older....
ALL diesel engines on OR off road over 25 horsepower now manufactured are equipped with tier 4 emissions, and yes that includes the DPF/DEF...and (you guessed it,) it sucks, a whole generation of tractor and off road techs have had to be trained on it.