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MTU 12V 2000 M94 Cylinder Head Gasket Failure

Discussion in 'Engines' started by T.K., Dec 7, 2020.

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  1. mapism

    mapism Senior Member

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    It just popped to my mind that I have a copy of it in my files.
    It's specific for series 183 engines, which are different animals, but I'd expect MTU to follow the same approach throughout their range, on a topic like this. Below is the relevant abstract for the first service on new engines, and it doesn't mention heads retorque.

    Elsewhere in the maintenance program, they do specify
    "cylinder head: remove, check valve, valve guide, valve seat, valve steam"
    but that's only for maintenance echelon "W5", which for 183 engines is every 3000 hours.

    __________________________
    MAINTENANCE TASK SCHEDULE:

    · one-time operations after the FIRST 50 operating hours with a NEW ENGINE
    · after W5 maintenance or after W6 major overhaul

    1. attachments check tightness of securing screws and nuts
    2. valve gear check valve clearance
    3. fuel pre-filter clean /replace filter elements
    4. fuel duplex filter replace filter elements
    5. engine coolant pump check relief bore for obstruction
    6. coolants pump check v-belt condition and tension
    7. engine oil change
    8. engine oil filter replace filter elements
  2. NYCAP123

    NYCAP123 Senior Member

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    I'm surprised and happy to hear that your insurance is covering the repair. To be honest it's far from unusual to see a seeping head gasket in less than 4 years or 800 hours, and not brand specific. Two things I'm curious about though are 1) are these bolts torqued by robotics, people or not at all, and 2) do most manufacturers require retorqueing at specific intervals? Any mechanics or engineers have those answers?
  3. Beau

    Beau Senior Member

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    I believe it was part of the MAN schedule?
  4. T.K.

    T.K. Senior Member

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    Thank you NYCAP. I am also curious to read the replies to your 2 questions. I can find no reference in the manuals to retorquing head bolts on MTU engines.
  5. d_meister

    d_meister Senior Member

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    Interesting failure, in that it's oil and not coolant. I have to wonder how there can be rust in the guide dowel area, but I'm more disposed to looking in the area of the lubrication system as the precursor of the oil leaks, something on the order of stuck pressure relief valve or a clogged gallery. Especially since there are no overheating episodes in memory despite head gasket failure allowing oil to leak on multiple cylinder heads.
    I don't know specifically about these series of engines, but virtually all modern cylinder head assembly methods use angle-torquing or use torque-to-yield fasteners. These methods are a one shot approach at achieving maximum clamping force, and cannot be re-torqued, as the initial set point of torque before angle torquing cannot be regained, and in stretch-to-yield fasteners; they're a one use fastener. I would guess that these head bolts are a one-use fastener in the eyes of the manufacturer, but may spec a re-use criteria and you should certainly verify that the correct procedure is being followed.
    Here is a link with some specs for the MTU-2000, which indicates that the procedure for setting head bolts is the angle-torquing method and that there is a maximum allowable elongation of the head bolts:
    https://barringtondieselclub.co.za/mtu/mtu-2000.html

    MTU 2000 Cylinder Head bolt torques
    Max shaft length = 212 mm
    Step 1 = 10 Nm
    Step 2 = 50 Nm
    Step 3 = 100 Nm
    Step 4 = 200 Nm
    Step 5 = +90 degrees, +10 degrees
    Step 6 = +90 degrees, +10 degrees
  6. Capt J

    Capt J Senior Member

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    I’ve seen a lot of it, I’m making the diagnosis by looking at the stain pattern on the head gasket. But willing to bet the deck of the block isn’t flat. Put a sheet of glass on it to check
  7. T.K.

    T.K. Senior Member

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    Thanks for the information Meister.

    If angle torqued cylinder heads bolts which is the case in these MTU engines cannot be re-torqued after a number of years or operating hours then it is impossible to suggest that retorquing the cylinder head bolts should have been implemented as part of the engine preventative maintenance schedule in order to avoid this failure.

    If MTU cannot prove that the engine has been subjected to any unusual operating conditions, then these cylinder head gaskets can have only failed as a result of gasket material failure or cylinder head bolt torque failure.
    Last edited: Dec 9, 2020
  8. mapism

    mapism Senior Member

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    I would agree with your conclusion on the possible alternatives.
    Theoretically, the non-straight deck of the block that CJ suggested is a third possibility.
    But it's hard to imagine that it took 800 hours to develop the leak, if that would be the reason.
  9. mapism

    mapism Senior Member

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    Well, if it was I never heard of it, and I'd be genuinely interested to see some MAN tech doc mentioning it, if you can get hold of it.

    BTW, the MTU schedule from which I made a cut and paste in post #21 is referred to their 183 engines.
    And back in those days, both MAN and MTU used to marinize the very same blocks, sourced from Mercedes-Benz (who called them OM 400 series).
    So, I couldn't think of any logical reason why they wouldn't have followed the same maintenance schedule, for non-marinized parts like the heads.
    Then again, I can't be positive that they didn't...
  10. olderboater

    olderboater Senior Member

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    Actually winter temperatures in that area of Italy often are in the low to mid 30's at night and occasionally less. Normally warm enough during the day though to avoid any freezing. In January, before delivery to you, there were several nights in the 20's with a lot of 27 degrees. Still I doubt it was cold enough for long enough to cause this issue.

    My first thought was water rather than freezing.
  11. Beau

    Beau Senior Member

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    I'm recalling work that was done about 20 years ago. It was meant to be anecdotal not definitive. I could very well be in error as my question mark (?) hopefully indicated. I'll see if I have any paperwork on it when convenient. The fact that you never heard of it falls into the cylinder cut out category, IMO. Did I wrong you in another life?
  12. NYCAP123

    NYCAP123 Senior Member

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    I can just imagine MTU or any other diesel manufacturer advising 'Don't subject to cold temperatures'.:(
  13. mapism

    mapism Senior Member

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    How touchy. What you said just made me curious to understand better, nothing else.
    If I would have thought that you were making that up, I wouldn't have even bothered asking.
  14. Beau

    Beau Senior Member

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    That's correct, I'm in "touch" with my feminine side, so be gentle with me ....
  15. mapism

    mapism Senior Member

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    Roger wilco. :)
  16. T.K.

    T.K. Senior Member

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    The engine block deck is perfect. It might just be an illusion in the image.
  17. ChiTown

    ChiTown Member

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    I would focus on the bolts. Are they one uses as described in post #25? If so, then replace. Also, there could have been a bad lot due to metallurgical/heat treating issues and they stretched/yielded? Regardless I would replace them with all else being accounted for.
  18. Donzi 54

    Donzi 54 Member

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    If they are stretch bolts they will need to be replaced. They are a one time use
  19. T.K.

    T.K. Senior Member

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    The cylinder head bolts are torque-angle bolts. The original bolts were measured and the shaft length was below the max. length of 212mm.
  20. Capt J

    Capt J Senior Member

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    Well, something went seriously wrong here. It's all localized to one side of the block and 3 joining cylinders. If you're sure of no overheating and not run WOT for a specific length of time. Sure the deck of the block is straight. It rules out a few things. Is the boat over-propped? Excessive exhaust back pressure, or exhaust gas temperatures on that bank? Bad turbo bypass and over-boost on that bank of cylinders?