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Detroit 671 TI rebuild

Discussion in 'Ocean Yacht' started by Boomer, Jun 26, 2018.

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  1. Capt J

    Capt J Senior Member

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    Or a bad injector tube or 2.
  2. Capt Ralph

    Capt Ralph Senior Member

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    YEP.
    I hate to ad, new or rebuilt heads mean nothing. Poor seating, shaping (reaming) and after lunch Friday (lack of testing) will fail a new injector tube.
    That is why I recommend pulling the side covers off.
    If a 4V reman head, could be cracked.

    I hope you did not re-use your original head.
  3. Boomer

    Boomer Senior Member

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    Rocker bridge pin failed....whatever that is...apparently a Friday after lunch failure to pressure test
  4. Ormond Bert54

    Ormond Bert54 Senior Member

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    That's the same thing that happened to my fresh overhauled 12V71TI several years ago. The rocker bridge pin is pressure fit and there is anti-freeze flowing under it. Mine loosened on the new cylinder head and my fresh overhaul was toast at 71 hours.
  5. cleanslate

    cleanslate Senior Member

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    Ugh...would make me sick. Was this the mechanic's fault; should it be checked out during the rebuild while things are apart for inspection? or is that not the case.
    Or did you have to eat it? And take it and like it....?
  6. Boomer

    Boomer Senior Member

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    I was lucky...when she ran low on coolant and started to heat up I caught it early and shut it down...added water and temp went down and then went up again...no more coolant...shut it down again and limped backed to port...found oil emulsified and called mechanic back...maybe shop didn't pressure test when rebuilt...maybe corrosion...maybe too many hot/cold cycles...everyone pointing fingers elsewhere...prove it...went with threaded pins (now called for in bulletin) and no more issues...and yes I ate it, liked it, and didn't even get a kiss on the cheek when done
  7. Boomer

    Boomer Senior Member

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    who did you head? Godwin Singer did mine...
  8. Ormond Bert54

    Ormond Bert54 Senior Member

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    It seems like pressure testing would be a good idea after overhaul. (pressuring the fresh water cooling system). This is how the problem was discovered after finding coolant in the oil. In my case, the shop refused to take responsibility for the $65k in hull overhaul that failed at 71 hours. The cylinder head was not a Detroit Diesel certified part (because Detroit didn't have any cylinder heads available at the time) so, out of all the parts I purchased for overhaul, this is one of the parts that was not a Detroit Diesel OEM part. Anyway ... just bad luck and disreputable shop. Ultimately, there was even more wrong with that engine though ... eventually replaced the entire block after 2 additional failed overhauls due to the liners not seating properly. I think we are good now.

    I also learned to remove the engine or trans to do the overhaul. It's just a far better way to do it.
  9. Boomer

    Boomer Senior Member

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    I feel for you...I really do...all that time with the hatches up and a mess everywhere...we did and overnight pressure test and no change so I hope and pray we are good...what causes the liners not to seat property? warped block?
  10. Ormond Bert54

    Ormond Bert54 Senior Member

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    Mine was a new replacement cylinder head. I forget where it came from. That was 2010.
  11. Boomer

    Boomer Senior Member

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    Got it...I had mine rebuilt and warrantied but they still didn't cover warranty saying it was the mechanics fault
  12. Ormond Bert54

    Ormond Bert54 Senior Member

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    Bad metal? I'm not sure what caused it ... potentially severe overheating before the initial overhaul. (I purchased the boat with one engine in need of overhaul). Eventually, we were sure that the cylinder liners had been carefully fit and when they came up with one cracked and several with a horrible fit, it was finally time to make a drastic change and get a fresh block.

    I have had things fixed things 3 times before putting a problem to rest on more than one occasion.
  13. Capt J

    Capt J Senior Member

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    They make liners for a 12v71 in 4 different sizes. I had one rebuilt where some took a #3, others took a #2, etc. that particular motor came apart at 150 hours after overhaul from a Detroit diesel dealer and they had used all #2 liners and some were loose.
  14. Ormond Bert54

    Ormond Bert54 Senior Member

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    Yes ... we were aware of the different sizes of liners. At the initial overhaul, there was discussion that if the sleeve didn't fit well (out of round), it might make the in hull overhaul difficult or impossible. At each successive overhaul, the technician would complain "who fit these liners"? "Terrible job...".

    It wasn't until the same shop overhauled the same engine twice that there was no question that there was a reason that perfectly fit liners turned up loose and cracked. I think the problem is solved now.
  15. Capt Ralph

    Capt Ralph Senior Member

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    Honing the block lung hole and hand fitting dry Detroit liners is an art. Not many left walking that can properly do this anymore.
    Last edited: Dec 21, 2018
  16. Capt Ralph

    Capt Ralph Senior Member

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    Here again is the problem; Just another wrench swinger & just an other MM machine shop.
    Two or more sets of eyeballs that should of known about the bridge pin (& other idiosyncrasies) and checked it before the head left the machine shop AND before bolting it down.
  17. Capt Ralph

    Capt Ralph Senior Member

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    I'm not sure if Detroit Diesel 2 stroke engines will ever fade away or die.
    It's going to be the old white hair guy in the back of the shop, the last real DD techs, that are dying off sooner.
  18. cleanslate

    cleanslate Senior Member

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    Was waiting for you to chime in; That's what I thought.
  19. cleanslate

    cleanslate Senior Member

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    Sad ,but true. I'm going back to 1992 or so , 8V71 went bad on us at Fernandina Beach on our way up north from Daytona to the Chesapeake .
    My Dad got some one local recommended to us by the local marina and yeah he was missing a tooth or two and had grey or little hair etc, he was able to figure out the problem though...water leaked into the top of the cylinder heads... hole in riser . Plus knew what he was doing.

    Then in 2001 I got my 6V53 overhauled and the young guy, 30ish, I contracted with brought in this older odd looking gentlemen 65/70 to work along side with him to do the onboard overhaul, which went very well.

    Both men were as you say, Capt Ralph.

    The guy I use now has 30 years at J&T N.J. under his belt, he's good but needs encouragement from time to time. And he's young! 59...:D
  20. Capt Ralph

    Capt Ralph Senior Member

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    Ah another good kid. yep, those young-uns need a flame in the correct place from time to time. Keeps their eyes clear and fanny warm.