>>>>> CRD VALVE FAILURE METAL ANALYSIS FINAL REPORT <<<<<

layback40 · **Posted:** Fri Jan 04, 2019 5:06 pm

From what I see in pictures on here & other places, the EGR looks exactly the same. I dont know if there is some internal differences though. It makes sense for VM to make one EGR system & provide one engine.
No one has commented on the poor quality diesel sold in the USA. It has caused engine failure on European designed engines. Google 'rod bender' if you are unaware.

mass-hole · **Posted:** Fri Jan 04, 2019 8:31 pm

layback40 wrote:

From what I see in pictures on here & other places, the EGR looks exactly the same. I dont know if there is some internal differences though. It makes sense for VM to make one EGR system & provide one engine.
No one has commented on the poor quality diesel sold in the USA. It has caused engine failure on European designed engines. Google 'rod bender' if you are unaware.

The US does have unique tuning though. The rate at which the EGR is used could be higher to meet US specific emissions.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

mass-hole wrote:

layback40 wrote:

From what I see in pictures on here & other places, the EGR looks exactly the same. I dont know if there is some internal differences though. It makes sense for VM to make one EGR system & provide one engine.
No one has commented on the poor quality diesel sold in the USA. It has caused engine failure on European designed engines. Google 'rod bender' if you are unaware.

The US does have unique tuning though. The rate at which the EGR is used could be higher to meet US specific emissions.

Another difference between North American market KJ Liberty CRD engines and KJ Cherokee CRD engines is the operating temperature of the engine. layback40 can probably confirm this for his local market, but all other markets around the world have engines that run with valves inside thermostat assemblies that start to open at 195 degree Fahrenheit. In North America, the engine thermostat assemblies have valves in them that start to open up at 176 degrees Fahrenheit.

This low operating temperature may achieve the low NOx pollution level the EPA demands, but it makes a bad situation even worse regarding the accumulation of pollutants inside the North American CRD engines. Compounding this problem is that a lot of North America has a colder climate than in places like South Africa.

geordi · **Posted:** Sat Jan 05, 2019 5:00 am

WWdiesel - if there is any soot scouring or exfoliation of the exhaust valves, it would have to be seen on an electron microscope. I don't think there is an argument to be made for that weakening the material strength of the stem by simply reducing the diameter, as that would have to be a VISIBLY narrower result to weaken it enough to separate in the way they do.

Like making a log out of play-doh and stretching it, the weakest point will narrow considerably before failure. This has not happened or been observed in any case that I am aware of.

Neither has there been any suggestion of warping / twisting / binding of the stems in the valve guides - as this would ALSO show visually as a wear indicator before failure. The point of failure has always been in the alloy, a section of the stem that DOES NOT ENTER THE GUIDE AT ALL.

Now if there was bending / warping on the guides for whatever reason and it was sufficient to slow the valve JUST ENOUGH that the piston could "assist" it to close... That continual ticking or tickling of the valve might be enough to weaken it. But I would think the contact wear on the piston would be seen as well - and nothing presented as obvious marking or polishing on the ones that I disassembled.

I have no knowledge of the EGR programming outside of the USA, but I remember hearing from (I think it was GDE) years ago that the USA programming for the EGR has the valve open at least partially under about 90% of throttle conditions - Only heavy throttle application causes it to close, and even then - the instant you let off the power, the thing opens right back up again.

With newer diesels such as the VW system that had the recall just recently, they actually have invented a way of having EVEN MORE EGR use than the Jeep CRD... The Jeep has a "low pressure" system that cannot overcome the turbo. The VW system has TWO different EGR paths, one of which is a "high pressure" EGR that routes the exhaust manifold DIRECTLY INTO THE INTAKE. Mother of Mazda, what a horrible system. The engine is ALWAYS 100% of the time injesting its' own already-burned soot... And if that wasn't enough, then they programmed it to inject WAY MORE fuel than it ever needed to run... To "make less emissions" by running the pre-turbo EGT over 1000 degrees during most operating speeds too.
"unfixing" all of this thankfully is still not that complicated, and the result is a car that had been getting about 37mpg on the highway is now registering 52mpg. I don't know for certain if that number will hold when I do a mileage test, but I hope so. It feels so much better and less restricted now, even without a power increase in the tune.

The point of all that - We as the end users have NO IDEA what they were thinking when they did these EGR programs... But whatever we think we have discovered, it would seem the truth is far worse: that they just haven't figured out how to destroy the engines any faster and they can't just outlaw them altogether... So making them so wasteful and inefficient seems a compromise in their eyes.

layback40 · **Posted:** Sat Jan 05, 2019 9:26 am

geordi wrote:

WWdiesel - if there is any soot scouring or exfoliation of the exhaust valves, it would have to be seen on an electron microscope. I don't think there is an argument to be made for that weakening the material strength of the stem by simply reducing the diameter, as that would have to be a VISIBLY narrower result to weaken it enough to separate in the way they do.

Like making a log out of play-doh and stretching it, the weakest point will narrow considerably before failure. This has not happened or been observed in any case that I am aware of.

Neither has there been any suggestion of warping / twisting / binding of the stems in the valve guides - as this would ALSO show visually as a wear indicator before failure. The point of failure has always been in the alloy, a section of the stem that DOES NOT ENTER THE GUIDE AT ALL.

Now if there was bending / warping on the guides for whatever reason and it was sufficient to slow the valve JUST ENOUGH that the piston could "assist" it to close... That continual ticking or tickling of the valve might be enough to weaken it. But I would think the contact wear on the piston would be seen as well - and nothing presented as obvious marking or polishing on the ones that I disassembled.

I have no knowledge of the EGR programming outside of the USA, but I remember hearing from (I think it was GDE) years ago that the USA programming for the EGR has the valve open at least partially under about 90% of throttle conditions - Only heavy throttle application causes it to close, and even then - the instant you let off the power, the thing opens right back up again.

With newer diesels such as the VW system that had the recall just recently, they actually have invented a way of having EVEN MORE EGR use than the Jeep CRD... The Jeep has a "low pressure" system that cannot overcome the turbo. The VW system has TWO different EGR paths, one of which is a "high pressure" EGR that routes the exhaust manifold DIRECTLY INTO THE INTAKE. Mother of Mazda, what a horrible system. The engine is ALWAYS 100% of the time injesting its' own already-burned soot... And if that wasn't enough, then they programmed it to inject WAY MORE fuel than it ever needed to run... To "make less emissions" by running the pre-turbo EGT over 1000 degrees during most operating speeds too.
"unfixing" all of this thankfully is still not that complicated, and the result is a car that had been getting about 37mpg on the highway is now registering 52mpg. I don't know for certain if that number will hold when I do a mileage test, but I hope so. It feels so much better and less restricted now, even without a power increase in the tune.

The point of all that - We as the end users have NO IDEA what they were thinking when they did these EGR programs... But whatever we think we have discovered, it would seem the truth is far worse: that they just haven't figured out how to destroy the engines any faster and they can't just outlaw them altogether... So making them so wasteful and inefficient seems a compromise in their eyes.

Geordi,
The reason I advanced the idea of soot sticking to the valve was that if it did & then under lean conditions, it burned, this could provide the sort of temperature necessary to cause the grain size increase that was seen. I would have expected that with the EGT's seen on these engines there would be enough heat transfer (cooling) between the stem & the valve guide to keep the lower alloy part of the stem cool enough to prevent grain enlargement.

WWDiesel · **Posted:** Sat Jan 05, 2019 12:35 pm

layback40 wrote:

geordi wrote:

WWdiesel - if there is any soot scouring or exfoliation of the exhaust valves, it would have to be seen on an electron microscope. I don't think there is an argument to be made for that weakening the material strength of the stem by simply reducing the diameter, as that would have to be a VISIBLY narrower result to weaken it enough to separate in the way they do.

Geordi,
The reason I advanced the idea of soot sticking to the valve was that if it did & then under lean conditions, it burned, this could provide the sort of temperature necessary to cause the grain size increase that was seen. I would have expected that with the EGT's seen on these engines there would be enough heat transfer (cooling) between the stem & the valve guide to keep the lower alloy part of the stem cool enough to prevent grain enlargement.

I agree in order to see microscopic exfoliation of the exposed valve stem area, it would have to be seen under an electron microscope?
But another question I have pondered is what are the chemical affects the exposure to the high carbon content of the combustion gases may have on the exposed valve stem metallurgical composition over enons of cyclic life of the valve. I am not a chemical engineer, but when the high soot loading is exposed to the high pressures of the combustion process which includes high EGT's, what does it become chemically and can it have any possible effects on the exposed valve stem area and maybe contribute to grain elongation as shown in the report?

I agree with your synopsis on the valves making contact with the piston that if so visible indication would be very prevalent in the piston top.
And further agree that any EGR system on a diesel engine is detrimental to their longevity and their overall efficient operation. That is why it should be totally disabled or removed on this engine ASAP if you still have one in operation. It is also the reason I hang on to my noisy 98 Dodge Cummins that came from the factory with no EGR, CAT, or CCV system of any kind from the factory.

But we know emission control proponents care little about engine longevity or efficiency! :furious:

Mountainman · **Posted:** Sat Jan 05, 2019 2:21 pm

Another difference between the EU models and ours are the turbos. How does that affect our EGT's?

Also, the soot clogs the intake, reducing flow. Might that make EGT's skyrocket under certain conditions?

I doubt the London taxis 2.8's have different valves (?), and they went 500k miles. I think we'll be fine with no egr... and to support that argument, there are several unmodified US versions that have exceeded 300k. Might their egr's be stuck closed, or not driven in the conditions that cause high EGT's, like basically all highway at low load (rural midwest)???

WWDiesel · **Posted:** Sat Jan 05, 2019 2:53 pm

Mountainman wrote:

Another difference between the EU models and ours are the turbos. How does that affect our EGT's?
Also, the soot clogs the intake, reducing flow. Might that make EGT's skyrocket under certain conditions?
I doubt the London taxis 2.8's have different valves (?), and they went 500k miles. I think we'll be fine with no egr... and to support that argument, there are several unmodified US versions that have exceeded 300k. Might their egr's be stuck closed, or not driven in the conditions that cause high EGT's, like basically all highway at low load (rural midwest)???

All very good points Mountainman, and layback40 in Australia brought up another good one on fuel quality/properties differences here in the US versus other countries and their possible long term effects on this engine. :ALONE:

That ultra low sulfur stuff they are feeding us may be a contributing factor to the problem?
I think I will look into adding an EGT (pre turbo pyrometer) gauge next if I can find some place to mount it that I like.
Don't care for the inside the vent mounts as we need all the air flow we can get here in the hot and humid summer time

layback40 wrote:

I thought the A428 was the ENS engine & came out in the non USA market with the KK. That is the case here. So we are at 10 or 11 years. I believe that fuel plays a part. Here in Australia there are 2 main suppliers of fuel, either diesel out of the Exxon refinery in Singapore or a large refinery in India (Shell?). I know when I change from one to the other I see a significant change in EGT in my XJ that has a VM425. I suspect what I am seeing is the difference between EU & US spec diesel. The KJ that I have with a engine failure spent much of its life on US spec diesel.

vwroad87 · **Posted:** Sat Jan 05, 2019 3:00 pm

@WWDiesel I want to add an EGT as well and I have the same issue of gauge placement. Interested in what you figure out. The main thing I took away from the analysis is that the metal grain size expands above 600C (1120F) so it's imperative to have engine cooling working 110% So glad I installed an HDS system with my brand new head.

WWDiesel · **Posted:** Sat Jan 05, 2019 3:24 pm

vwroad87 wrote:

@WWDiesel I want to add an EGT as well and I have the same issue of gauge placement. Interested in what you figure out. The main thing I took away from the analysis is that the metal grain size expands above 600C (1120F) so it's imperative to have engine cooling working 110% So glad I installed an HDS system with my brand new head.

I will post once I get it all figured out and installed.
To add to what you stated, I agree that a good functioning cooling system is imperative, but EGT's can be negatively affected by several other factors as well, such as fuel quality, boost pressure, air inlet temperature to head (post CAC), Air filter cleanliness factor, quantity of fuel injected, exhaust backpressure due to restrictions (CAT, Muffler) etc....just to name a few.

geordi · **Posted:** Sun Jan 06, 2019 2:40 am

Reduce exhaust backpressure is a big one - But also increase the boost without increasing the fueling, and that will reduce the EGT at the same time.

GordnadoCRD · **Posted:** Sun Jan 06, 2019 6:21 am

^^^^^^^^
What he said.

otrbreakdown · **Joined:** Sat Feb 20, 2021 9:21 am **Posts:** 11

Hi there did anyone can give the exact valve spring diameter on a 2.8 CRD ?

>>>>> CRD VALVE FAILURE METAL ANALYSIS FINAL REPORT <<<<<

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