4MG Rebuild

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Oxbow, Feb 19, 2024.

  1. Oxbow

    Oxbow Road Train Member

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    A lot of you have shared their rebuilds, so I suppose that I should as well. I will be relying on advice from the forum. @wore out has helped me numerous times in the past, and I hope he is willing to do so when he has time on this one. I AM NOT A MECHANIC! Hopefully @Last Call can help as well.

    Backstory: I have a 4MG that only has about 100,000 on an out of frame rebuild. Unfortunately the block developed a crack that I was unable to patch up. I tried JB Weld, then brazing, then finally welding with nickel rod, and the crack would reappear each time and extend a little further. I did not try Lock and Stitch because the crack entered an oil gallery, and I could not control metal shavings getting into the oil. We have another truck that also has a 4MG, but it is not speced for heavy haul and has an aluminum frame that was not going to be able to pass an annual inspection soon. So, we pulled the 4MG out of the lowboy tractor (blue), and then pulled the 4MG out of the aluminum truck (white) and transplanted it into the lowboy tractor. In the mean time I bought a rolling chassis (89 379 with the same gearing as ours, and it had a 4MG that would run but had a miss. The idea was to rebuild the donor block from the rolling chassis with the parts from the blue truck.

    We are now tearing into the donor block and getting ready to rebuild it. This morning:
    upload_2024-2-19_19-1-42.jpeg

    This evening:
    upload_2024-2-19_19-2-29.jpeg

    All three of these engines have retarders. Ever wonder what a retarder looks like?
    upload_2024-2-19_19-4-4.jpeg
    Engine side:
    upload_2024-2-19_19-5-0.jpeg
     
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  3. Last Call

    Last Call Road Train Member

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    Be glad to do what ever I can to help @Oxbow I’am just a ph call away you know that Your a mechanic I’ve seen your helpful in put before you have nothing to worry about
    BTW good of you to start a thread like this it may be helpful to others
     
  4. Oxbow

    Oxbow Road Train Member

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    The seller of the donor engine stated that it had a miss. I didn't care because we are going to rebuild it anyway. Cylinders 1,2,3
    ,4, and 6 all looked like this:
    upload_2024-2-19_19-8-24.jpeg
    We fired it up before removing it from the rolling chassis frame, and # 5 was the dead cylinder. After pulling the head we confirmed the miss. Here is #5:

    upload_2024-2-19_19-10-41.jpeg
    We are going to continue to strip the block, get it hot tanked and the lower liner bores re-sleeved, and start putting the newer part from the engine out of blue into this block. Plans may change, but that is the plan for now. All stock parts except for the turbo.

    Am I a fool? Should I rebuild with new cylinder packs? Maybe go to custom build with different parts? To be honest, the engine out of the blue truck runs really well, and has enough power for our needs (probably 475 to 500 if I were to guess).
     
  5. Oxbow

    Oxbow Road Train Member

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    Thank you sir!
     
  6. AModelCat

    AModelCat Road Train Member

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    Block sure looks a heck of a lot like the 92U I've got.
     
    Feedman, broke down plumber and Oxbow Thank this.
  7. Oxbow

    Oxbow Road Train Member

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    No mechanic here, just ###### lucky to have the full manual from Cat! It took us awhile to figure out how to properly remove the retarder without screwing things up.
     
  8. Oxbow

    Oxbow Road Train Member

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    Pretty similar I imagine.
     
    Feedman and broke down plumber Thank this.
  9. Last Call

    Last Call Road Train Member

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    Anytime what’s the target date for completion ?
     
  10. Last Call

    Last Call Road Train Member

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    That can be interesting lol
     
  11. Oxbow

    Oxbow Road Train Member

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    One of the questions I have:

    We get it into the machine shop to have the lower bores sleeved, the deck cut, and counter bores cut. Do they just keep cutting the counter bores until all signs fretting is gone, or do I need to tell them how much? I suspect the machine shop will know, but this is new territory for me.
     
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