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.

We would never reuse stretch bolts over again on cylinder heads. Maybe they are non stretch head bolts

If I read the posts correctly the heads have not been removed and the bolts are one-time-use. If they weren't damaged I understand not replacing them. 'If it ain't broke don't fix it'. Glad it turned out to be nothing more than a gasket replacement. It's what I expected and hoped for with the original post. As I said at the time motors overheat all the time from many causes. It doesn't make the motor toast unless ignored. I suspect your yard will be giving you VIP treatment from now on to help wash some of the egg off their faces.

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.

Logically ,It seems if these are torque to yield bolts and they are still within specified length, they were never likely torqued to yield (i.e. not fully / properly torqued down to begin with)

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.

Total agreement, something doesn't make sense.

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?

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!