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We a Krone Big X 770 (2016). It has twice had different valve heads replaced due to broken exhaust valves!
Man engine D2868 LE121.
This engine was also used by Claas. I understand that here too there was a problem! How was this resolved by Claas?
Has anybody else out there had this problem, and how was it resolved by Krone?
The OP from Krone says check valve clearance every 500 hours, but if it breaks after 300 hours!
 

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Where do they break at? You still have the broken ones around? Could you post pics of them or anything else you noticed that seemed odd? Has me curious.
 

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To me that looks like it is valve or valve seat failure. Without being able to inspect it closely, I'm gonna guess heat is involved. Has this engine be turned or tuned up above specs as in had more fuel dumped in the fire?
 

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Totally standard. Not changed anything else.
What do you think about fuel additives?
 

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Not sure if I have seen valves chip like that. Have seen burnt, but, that looks like chunks breaking off. I would say light valve springs and they bounce when they seat?? Totally a guess here. Lots of exhaust backpressure at the valve? I would take that to good automotive type machine shop and ask what they think. One that rebuilds lots of diesel heads. Tell them it isn't the first time. Looking at it again, the valves don't look centered on the seats? Take it to a good machine shop. I think there is something wrong from the start when it was built.
 

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Not sure if I have seen valves chip like that. Have seen burnt, but, that looks like chunks breaking off. I would say light valve springs and they bounce when they seat?? Totally a guess here. Lots of exhaust backpressure at the valve? I would take that to good automotive type machine shop and ask what they think. One that rebuilds lots of diesel heads. Tell them it isn't the first time. Looking at it again, the valves don't look centered on the seats? Take it to a good machine shop. I think there is something wrong from the start when it was built.
I think we are seeing pretty much same thing, something about how that valve is landing on the seat, don't appear it is ever making contact with piston. I have never seen one come apart like that either without other factors involved. That was why I asked about possible over fueling creating more heat than designed for, but owner says no. Wonder if it is simply they may had a batch of bad valves? You would think someone like Mann would be on top of that.
 

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Yeah wow that valve just looks like it was junk metal day.
How does the cam or the rest of the valve train look? Anything that could have been binding or a chunk out of the trailing slope of the lobe that could lead to uncontrolled motion closing?
 

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We a Krone Big X 770 (2016). It has twice had different valve heads replaced due to broken exhaust valves!
Man engine D2868 LE121.
This engine was also used by Claas. I understand that here too there was a problem! How was this resolved by Claas?
Has anybody else out there had this problem, and how was it resolved by Krone?
The OP from Krone says check valve clearance every 500 hours, but if it breaks after 300 hours!

What was done to repair the first occurrence of valve problems on this engine? Where there a number of valves with problems? And do you know if the one shown was replaced before? Four valve heads are very unforgiving if the valve guides are worn. The valve stems are slender and tend to have a lot of length extending through tall ports in the heads. A small amount of wear in the valve guide tends to cause the valve to close on the valve seat off centre.
 

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Discussion Starter #11
What was done to repair the first occurrence of valve problems on this engine? Where there a number of valves with problems? And do you know if the one shown was replaced before? Four valve heads are very unforgiving if the valve guides are worn. The valve stems are slender and tend to have a lot of length extending through tall ports in the heads. A small amount of wear in the valve guide tends to cause the valve to close on the valve seat off centre.
[/QUOTE
Both times the valve head has been replaced as a complete unit.
This last time I didn't take the valve head apart! The first one had worn valve guides and stems! I would imagine the second one is the same! Cylinder 1 was the first, cylinder 8, this time around!
 

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I am by no means an expert but I have seen a number of valves that have contacted pistons for various reasons and have never seen even a chip of of the face of a valve . My guess is sub par valve material .
 

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It’s unclear what may be causing this without more knowledge. If the exhaust temperatures are too hot to maintain oil film strength between the exhaust valve stems and the valve guides, something would have to be done to reduce those temperatures.

That being said, it’s an odd configuration for an industrial engine. The thinness and sharpness of the circumference of the exhaust valves looks to be more performance oriented than striving for durability. That, combined with the skinny valve stems doesn’t allow much heat to sink from the valve, through the valve stem and the oil film into the valve guides to then escape into the head.

It’s also possible that these are titanium valves, I don’t know. If they are they will only have minor magnetic attraction. There is a world full of motorcycles that were built with titanium valves and hardened steel valve guides. That combination of metals seems to be prone to premature wear. One solution for titanium valves is to use bronze valve guides. Bronze valve seats can also be used in motorcycles to prevent the hardened seat face from wearing the titanium valve. This along with hardened coating on the lightweight valve eliminates frequent adjustments of valve lash because it has worn the clearance to zero or less.

A better solution I feel, is to use stainless steel or steel valves in the hardened guides and seats, but this generally requires slightly stronger valve springs than titanium valves do to prevent valve floating or bouncing. I’m not stating that your engine has titanium valves, I’m just implying that it might, based on the early failures and strange metallurgy in the broken valve photo. When they are telling you to adjust the valve lash every 500 hours, something’s up, and it ain’t good. You now have two spare heads to do up properly though. I just don’t think you’ll get lucky enough to fix as fails on all eight heads without hurting a piston or a cylinder liner.😕

Valve head number 8
 

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That’s a negatory on the valves. That’s a step down vs inconel and just won’t stand up on a turbo diesel. Same reason the turbo turbine is inconel. That just looks like a bad batch to me. Probably don’t want to hear it but I’d get new valves in all those heads.
 

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Claas pretty much recommends valve adjustment with every oil change on their orange harvesters

I hope the younger generation doesn’t think things like that are normal. I put new head gaskets in an Allis Chalmers 8550 with 10,000 hours on it, when I went to reset the valves they were all still set perfectly, and it has four valves per cylinder. It’s 39 years old.
 

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Discussion Starter #17
Claas pretty much recommends valve adjustment with every oil change on their orange harvesters
Other than the quote from the op manual do you have anything else regarding the valve adjustment? Maybe from a claas dealer/technician
 

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I had an identical failure on an Allis engine. I had the head done up and they had touch the valve grinding stone on the back of the valve ( you could see a line ) and they broke at that line.
Duetz engine require regular valve adjustments but to my knowledge didn't give trouble
 

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I hope the younger generation doesn’t think things like that are normal. I put new head gaskets in an Allis Chalmers 8550 with 10,000 hours on it, when I went to reset the valves they were all still set perfectly, and it has four valves per cylinder. It’s 39 years old.
You must have done a lot of things right to keep one of those running this long!! Mine is still running great, with a 855 Cummins. They had an early version of valve rotators IIRC?? Good engine. Too much rpm.
 
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