MTU 12V 2000 M94 Cylinder Head Gasket Failure

MTU stated that the cylinder head bolts had not reached max shaft length and there was no requirement to replace them. MTU asserts that these cylinder head torque angle bolts cannot and should not be re-torqued?

WHY would they re-use the cylinder head bolts after a catastrophic failure such as this??? I would'nt have even considered re-using the head bolts after this failure.

I agree with Capt J. Given the scope of work involved my preference would be, out an abundance of caution, to use all new replacement parts, especially when there’s some uncertainty regarding the specific cause. Once the engine is opened up use the opportunity to address all the potential variables.

This has been an interesting post, thank you for sharing. I’ve been following it because of my own experience with one of my Cummins. Fortunately I was under warranty and Cummins was terrific. All new replacement parts.

I hope that your issue has been successfully resolved.

I remember talking with a JD tech. On the larger JDs, new stretch bolts every time.
They are not torqued down, degrees of turns are measured in the final head bolt tightening regiment.
I have never done this or witness this myself so I'm sure there is more to this, but he did state; new head bolts every time.
This tech did mention, there is a special long taper on these bolts also.

So, now I'm confused, MTU says do not re-torque the bolts, I read that as stretch bolts.
MTU re-used the same head bolts, I read that a regular head bolts.

Next question, are these bolts or studs/nuts?

+1.
That's precisely what popped to my mind while reading the last TK post.

Angle torque, as specified by MTU brings the tension on a bolt to a specified level by first torquing to a known value and then turning the bolt a specific number of degrees. That achieves some bolt elongation and maximum calculated clamping force on the components. That is why they cannot be re-torqued, as you cannot go back to that initial torque stage and repeat it. If a bolt is turned loose to repeat the torque stage and then the angle torque finish, it may cause loss of clamping force and leaks, as well as achieving a stage of bolt elongation that can result in material failure.
Since there is some elongation, there is a re-use specification provided. The amount of elongation specification can prevent bolt failure while assembling, which can result in wasted parts and labor. I first encountered this process in 1973 when I was trained on the PRV (Peugot, Volvo, Renault) Volvo B27 engines. It's common, now, but still attempts to deal with the immeasurable, which is how much clamping force is actually achieved?
HERE is a very good explanation of what torquing bolts attempts to achieve.
The process of torque-to-yield as a specified process results in fasteners that cannot be re-used.

Darn good post.
Thank you.

Now I wonder, Was that head messed with before T.K. got the boat?

Well then, This leaves near only one last failure explanation;
Ship Happens..

Thanks to this thread I know more about bolt torquing and specifications for this application.
Very cool.
However, other than expenses, why not torque new bolts in light of the original idiopathic failure?
Other than expense.
Are we afraid the new boots are flawed?
Interesting.

With 800 hours, times 60 minutes per, times any arbitrary engine speed, let's say 1200 rpm= 57,600,000 revolutions, then divide by 2 (4 strokes = 2 revolutions) give us 28,800,000 detonations under each cylinder head. It's not looking probable that three cylinders began to leak oil due to incorrect assembly. Chances are slim that the engine would have made it off the test stand if they missed a step in assembly.
I hope the problem is solved and it's as simple as defective head gasket material. Call me stubborn, but I'll stay with my original WAG (Wild A**ed Guess) about sudden rise in oil pressure from a relief valve-type of issue. I don't actually know if they have a relief valve, though. Must have, no?

In these forums; That's SWAG:
Scientific Wild Asp Guess...

I'm sure they do have oil relief valves. That is not going to blow a head gasket on it's worst day though.
Steam or pressurized water will.
I think I commented that in post #51 and nobody bit into it.

Without re-reading the whole thread; if I remember correctly it is only an external oil leak, and no breach from coolant to oil or vice-versa. Also no coolant external leak. Oh, well, if trained technicians and the big guns at MTU haven't figured it out, chances aren't good for me doing it from here.

Ralph, thanks for the SWAT enhancement. My mother always said a good vocabulary is important, and you've improved mine, today!