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Mtu 4000 series cylinder head problem.

Discussion in 'Engines' started by vic13r, Feb 11, 2020.

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  1. vic13r

    vic13r New Member

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    Hi from Greece,this is my first post,I did not see threads for writing the first time.

    I have an cylinder head issue with mtu 16v 4000 series on a few generators not on a yacht (sorry for that),but I can t find a solution even from the dealers.My problem are the valve seats are disappearing after few hours,that happens all the time as the engines were new and after a full factory replacement about 2 year ago.
    Does anyone know a possible reason for that,thanks in advance.
  2. Capt J

    Capt J Senior Member

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    Fuel quality is a possibility. EGT's that are too high or load is too high, are another possibility. Bad valve seats, or something wrong with the geometry in the valve train on your engine, or bad valve adjustment can be another.
  3. vic13r

    vic13r New Member

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    I don't believe the seats have problem because they are machined from the factory and as I said before the heads are all changed with new from the factory ( 16heads x19 engines=304 heads) before 3 years, so far I have found about 50 heads with seat problem mostly on the exhaust.
    Can you explain me why the fuel quality can cause that problem, where can I find more information about that??Thanks in advance Capt J.
  4. Fiammetta42

    Fiammetta42 New Member

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    If it’s just the seat only and not the valve itself then I suggest the valve clearance of the exhaust valve is too close , ie not a wide enough gap .
    As they warm up and run well with EGT s and load for the generators because the exhaust valve is not quite shut or shutting fast enough gas escapes and over time the heat destroys the valve seat .

    Or the timings a fraction out .
    It may meet factory specs with the marks available but a batch of duff exhaust cams , cam gears means the E valve isn’t closing as it should at the right time .....staying open a bit .

    Or the E valve springs are not correct spec .You have not said if the original valve gear has been transferred across? Assume naked heads and they transferred everything across with the original closing error(s) ?

    what sort of hrs are we talking about?
  5. Fiammetta42

    Fiammetta42 New Member

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    How ever on reflection 304 heads in 3 yrs it’s unlikely to be a valve timing error so many times .
    Generators running UNDER loaded most likely .
    You need hight temps / reasonable high EGTs to get the best burn and highest concentration of “ protective “ by products .
    A low loads the protection is not there .
    There’s and old adage with diesels ( any ) “ run em hard “

    more here ....

    https://www.sciencedirect.com/science/article/abs/pii/S0043164896069451

    59C710D3-26DD-4A53-81E9-A13743BFC7DD.jpeg
  6. Capt Ralph

    Capt Ralph Senior Member

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    Good lead and contribution.
    Thx
  7. Capt J

    Capt J Senior Member

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    Pre-ignition/detonation will cause burned exhaust valve seats as well. So if the fuel is too high a cetane number and the engines are experiencing detonation it could cause what you're seeing. But having these failures among 19 different engines points to something that is common between all of them in your situation. Could be underloaded, could be poor fuel/lubricity, or etc. Also, MTU has been known to have a batch of inferior parts now and then that they let slip through the cracks and then tried to get out of warrantying later, but miraculously have an "updated part" when you buy a replacement part. First 150 sets of 16v2000's had piston rings stamped and installed upside down and many failures, however on one boat they tried to blame the crew saying they had too much oil in the engine, until another boat came to the same marina with the same engines and also had a major failure requiring overhauls in the first year and low hours.

    How many engine hours have these generators gone before having exhaust valve seat failures?
  8. vic13r

    vic13r New Member

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    Every part is bone stock,the cylinder heads 304 pcs changed from the official dealer for the maintenance sschedule 3D.The lash is 0.20mm 0.50mm,its simple I think,and made from 2 or 3 people. The engine hours were from 4000 to 6000,because the generators are 19 pcs and they haven t work all the same hours.What do you mean closing errors?
  9. vic13r

    vic13r New Member

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    The 304 heads replace due to maintenance chart 3D,not because damage, after that about 50 heads had failure.
  10. Fiammetta42

    Fiammetta42 New Member

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    “ closing errors “ I mean gas is prematurely escaping because the E valves are not tight enough closed within tolerable timing .
    How ever now you disclose 4/6 K hrs each that’s a different ball game in terms of getting to the aetiology of this .

    Then they ( 304 ) were replaced as routine of which 50 were found with issues .

    Coupled with Capt J ,s additional info on “ a batch of inferior parts “ ,my contribution of excessive low load hrs ( not enough protective layers forming ) and now yours hrs contribution I don’t think we are ever going to get a single definitive answer .

    eg if due to “ defective parts “ poor lubrications.......say a valve guide wears then the stem will move , kinda vibrates about = poor seal = gas getting round = prematurely wear etc etc + not quite the right fuel burning at low ish loads = inadequate layer or valve seat protection by products etc etc .....Then toss in 4000/ 6000 hrs ........chasing shadows.


    So the heads came off in routine maintenance....if I understand you correctly?
    If so what’s the problem ?
  11. vic13r

    vic13r New Member

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    The problem is that until now 50 heads of the 304 are failed,the 304 heads were precaution maintenance.
  12. Fiammetta42

    Fiammetta42 New Member

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    MAN s exhaust valve lash is 0.6 mm , the inlet is 0.5 .
    They tend to wear open ie get bigger hence the tapperty sound .
    The exhaust clearance is always larger because they heat up more and thus expand a bit more .
    But none of this is the cause btw ....assume the lash is set routinely, with MAN every 400 hrs ?

    How often have those MTU s valve had there valve lash checked / adjusted?
  13. Fiammetta42

    Fiammetta42 New Member

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    Right / Ok gotcha .

    Sorry I,am ( and suspect mist on here ) unfamiliar with the MTU service schedule.......thought the heads come off in routine maintenance.
    I now see your anxiety.
  14. Fiammetta42

    Fiammetta42 New Member

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    So let’s eliminate “ open E valve / bad timing “ as wear means they actually prematurely close as the gap widens .Power is lost as the gas mix is not optimised ...buts that’s not the issue here .

    I think we are back to low loading .....assuming none or little of Capt J contribution.
  15. Capt J

    Capt J Senior Member

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    Could also be weak valve springs and the valves are floating.
  16. Fiammetta42

    Fiammetta42 New Member

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    Agree .
    4/6 K hrs is about 10 years + normal leisure boating ....arguably near 20 years for some .So a big rebuild if they were in a boat wouldn’t really raise an eyebrow .
    Obviously in a industrial application.....and inside 2/3 years I can understand the OP dissatisfaction/ disappointment.
  17. d_meister

    d_meister Senior Member

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    Fiammetta42 may be on the right track with insufficient loading, or other operational issues. Bear in mind that vic13r said in his first post that the engines are used for generators. I'm guessing that with that kind of equipment he may be using them for an island/resort power supply? Those engines should be rated at over 2,000 KW.
    Still not clear is if the heads are supplied with installed valve, and, exactly what the failure is. Are the seats cast iron head material or inserts? Are the seats burning or mating poorly enough to affect compression? It would seem to me that combustion temperatures are too low, otherwise the discussion would be about valves instead of seats. Any valve material unable to transfer heat to the seat should be burning away if the engines are loaded.
    Interesting that the issue began with the installation of new replacement engines and that the factory has not become involved. The dealer should have brought them in. Some of the replacements should have been warranted, attracting the attention of the manufacturer or at least the distributor.
    Are the engines direct replacements for the previous installation, as the same make and model as the predecessors? If not, are there environmental issues like insufficient or cool enough intake air? A real concern may be exhaust flow, as in new engines bolted to an existing exhaust system designed for different engines.. Are the engines equipped with exhaust temperature alarms? Did the previous engines lead a happy life and die of old age, or were there issues with them, as well?
    What kind of fuel are they running on? Can there be a veg-oil blend? Is used motor oil added into the fuel?
    Interesting to get some answers, and maybe failed parts photos.
  18. Capt J

    Capt J Senior Member

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    The computer should be able to tell how they were loaded throughout their life. I'm not very knowledgable on the 4000 series but I think at 5-6,000 hours MTU calls for an upper end rebuild and a bunch of things, perhaps this is when the valve seats were noticed?
  19. d_meister

    d_meister Senior Member

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    Sure would like to see that generator plant! 19 engines! Generating European power @ 50hz, those things are maybe running at a steady 2,000 RPM? Maybe no electronics needed for constant duty gen power. Looking forward to some more info.
  20. vic13r

    vic13r New Member

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    The engines are rated at 1450kw at 1500rpm.The heads had come complete with valves and springs,the seats are cast iron and they dissapeared completely not just burned.The plant is a little tight from space,I know that's not good for the intake air but we cant do something for that.There are alarms for the egt and intake air temperature.The engines have not changed they are the same engines all the time only new cylinder heads have been replaced.
    Last edited: Feb 13, 2020