Perkins 4-108

Discussion in 'Diesel Engines' started by bob24, Dec 15, 2007.

  1. bob24
    Joined: Apr 2007
    Posts: 12
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    Location: Stonington, Connecticut

    bob24 Junior Member

    Hi;
    Have a rebuilt Perkins 4-108 with about 400hrs on it and yesterday on the SC ICW the alarm went off. Had less than 10lbs oil pressure on the gage and the oil pressure alarm was going off too. Each has it's own sending unit. Anybody got any ideas. Thanks, Bob
     
  2. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    BOTH ! engines went to 10psi at the same time?

    Look for a poor ground in the gage circuit.

    If only one , inspect the oil , and do a oil filter change .


    Let us know,

    FF
     
  3. bob24
    Joined: Apr 2007
    Posts: 12
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    Location: Stonington, Connecticut

    bob24 Junior Member

    Hi Fred;
    I didn't make myself clear. Have one engine and 2 sending units. Did an oil change and had no effect. Thanks for you input. Bob
     
  4. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 111, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Sounds like you lost a bearing. IF you can find an oil line (pump to filter?) you could measure the pressure there WITH A MECHANICAL GAGE! to see if its the oil pump output , or an internal fault.

    The oil pump it self is very reliable , But?

    FF
     
  5. bilgeboy
    Joined: Dec 2005
    Posts: 157
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    Location: Boston

    bilgeboy Senior Member

    I caught your drift.

    You are reasonably sure the oil pressure is low because the alarm circuit tripped AS WELL AS the pressure sending unit reading low. This is what you meant by “both.” You now think the drop in oil pressure is real because it was confirmed by redundant, independent circuits.

    I think you are right. You have a real drop in oil pressure. You did exactly what any boat owner should do…an oil change. This lets you inspect the oil as well as make sure that the pressure is not low due to low oil levels. I’m with you so far. You trust your gauge, so you are ready to make more interventions and then restart, judging success by the installed instrumentation.

    I have to sit back and watch, now. I like diesels, and like learning more about them, so all I can add is that I will read your thread with interest…and if the diesel gods allow, try some reading on the subject.

    Please post your findings so that we can all learn something,

    Thanks,

    Mike
     
  6. bilgeboy
    Joined: Dec 2005
    Posts: 157
    Likes: 7, Points: 0, Legacy Rep: 45
    Location: Boston

    bilgeboy Senior Member

    You didn't mention if you changed the oil filter as well...I assumed you did but you know what happens when we do that.

    I did get a chance to review the subject a bit. It looks like you need to make sure the oil pump is turning with the engine. The key or splines or whatever mechanism communicates the oil pump shaft to the gears (the "pump") themselves could be chewed up. Other than that, the sump pick-up needs to be checked out.

    Not a whole lot to go wrong.

    Please fill us in on your progress.

    Mike
     
  7. Frosty

    Frosty Previous Member

    Recently overhauled?????

    A failed pump would be zero pressure.

    Under 10?? check the pressure relief valve is not stuck open.

    It will be wide open at cold but if it stays open pressure will drop right off.

    Or youv'e turned a bearing.
     
  8. bob24
    Joined: Apr 2007
    Posts: 12
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    Location: Stonington, Connecticut

    bob24 Junior Member

    Hi Folks;
    Here is my friends update on his 4-108.
    For those mechanics/engineers out there, our problem turned out to be a sheared bolt for the idler pulley gear hub in the timing gear circuit; this loosened the retaining plate which relieved pressure from the oil channel which fed from the main oil gallery. Apparently, no further damage was done to the engine. This is surprising, given that the timing gears were loose and could have led to interference of the pistons and valves, and no oil was reaching the rocker arms which could have seized the rockers or the valves.
    Who would have guessed. Thanks for your response.

    Bob
     
  9. Frosty

    Frosty Previous Member

    Who found that? the guy that overhauled the engine.
     

  10. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 111, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    our problem turned out to be a sheared bolt for the idler pulley gear hub in the timing gear circuit

    Sounds like the "rebuilder" did not own , or understand the use of a Torque wrench.

    FF
     
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