12.7 no heat

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by nikmirbre, Aug 9, 2020.

  1. nikmirbre

    nikmirbre Road Train Member

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    B420367B-5363-4CFA-A655-43DDC757AFAC.jpeg 40A10DA3-8FA5-4133-9915-FBD1BFA94AB5.jpeg
    As title says no heat. I needed it this morning to help defog my windows. I thought I would turn the valves and it would help but none whatsoever. The 2nd picture, I turned that valve and coolant started pouring out of it.
     
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  3. nikmirbre

    nikmirbre Road Train Member

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  4. AModelCat

    AModelCat Road Train Member

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    If the line going to the core is hot and the return from the core is cold, there's likely a blockage somewhere.
     
  5. blairandgretchen

    blairandgretchen Road Train Member

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    Those valves are in the open position, so I’d agree on a possible blockage.

    Coolant shouldn’t pour out of a valve, so I’d assume that one is seized/broken/faulty.

    The one out of the head - does it go to transmission cooler? Leave that one alone.
     
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  6. blairandgretchen

    blairandgretchen Road Train Member

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    Try replacing with these style valves.


    A3556335-9F52-47E6-BFB6-FA180F61FBEF.jpeg
     
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  7. nikmirbre

    nikmirbre Road Train Member

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    I agree with blockage. How/where would I start??
     
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  8. nikmirbre

    nikmirbre Road Train Member

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    Yea it’s the valve is bad on that one. And yes my last Detroit had those style valves and I like those better! Gonna fix it this weekend to give me something to do
     
  9. AModelCat

    AModelCat Road Train Member

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    Usual suspect would be the water valve that regulates the coolant flow through the core. Those 1/4 turn valves could be stripped and not fully open too.

    Next suspect would be the heater core itself being plugged up.
     
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  10. bad-luck

    bad-luck Road Train Member

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    I don't remember how the heater core is set up, it's been years since I have owned a freightliner. But check to make sure the valve that is controlled by the climate control is opening
     
  11. nikmirbre

    nikmirbre Road Train Member

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    This is a w900 glider.....
     
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