12.7 Detroit cooling system

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Jasonar15, Jun 14, 2019.

  1. Jasonar15

    Jasonar15 Medium Load Member

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    i have a 1999 fld120 with 12.7 Detroit. The 2 small hose connectors on the S pipe after water pump and before oil cooler keep leaking. Have replaced them both. Could anything be stopped up causing pressure? I am changing thermostats tomorrow. Thanks
     
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  3. Rideandrepair

    Rideandrepair Road Train Member

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    Being silicone, they may seep a bit when new, especially when cold.Notorius problem on new Trucks, since going to silicone hoses. Commonly called a “ cold leak” eventually heat will seal them up. If you have good constant tension “silicone” style clamp that has an inner solid ring to protect the hose,and a spring loaded screw, sometimes they need to be torqued real good, and again later when hot, because the inner ring interferes with tightening.a one piece spring tension type works good also, unless it’s lost it’s tension. I have both types on mine, no leaks. Any excess pressure in system will always find the weakest point, be it a clamp or a weak oil cooler or a rusty tube, etc. As long as your not building pressure in coolant, I don’t think any obstruction is the problem, I doubt a plugged oil cooler or. even a stuck thermostat wouldn’t cause it, unless both thermostats we’re stuck closed. That would be rare.Also an obstruction that bad would probably cause it to run hot. My guess is you need to crank the clamps tight.
     
  4. Jrwinkles

    Jrwinkles Bobtail Member

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    12.7 need help figuring out what size short belt to bypass York Ac. Running alternator off of auxiliary drive.
     
  5. Jrwinkles

    Jrwinkles Bobtail Member

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    Is there a reasonable Mechanic in the Birmingham area that does weekend work?
     
  6. Jrwinkles

    Jrwinkles Bobtail Member

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    Specifically 12.7 Detroit 1996 FLD 120
     
  7. Jrwinkles

    Jrwinkles Bobtail Member

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    The 12.7 is a 1996 Detroit 60 series D DAC 3
     
  8. Rideandrepair

    Rideandrepair Road Train Member

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    Measure the distance with anything, a piece of string if you have to. T/As used to carry the exact belt for that reason. But an auto parts store should be able to match up something
     
    Jrwinkles Thanks this.
  9. Jrwinkles

    Jrwinkles Bobtail Member

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    Thanks Bro!
     
    Last edited: Sep 18, 2019
  10. Jrwinkles

    Jrwinkles Bobtail Member

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    Feb 1, 2019
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    I understand string now
     
    Rideandrepair Thanks this.
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