Detroit coolant issues

Discussion in 'Trucks [ Eighteen Wheelers ]' started by KittyKicker, Nov 11, 2019.

  1. KittyKicker

    KittyKicker Light Load Member

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    Dec 27, 2015
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    I have a 1998 12.7 Detroit that is pushing coolant out and the heat also quits unless you idle it up to about 1200 or more. I put a block tester on it, no bubbles and the fluid never changed colors. It did start overflowing coolant out of the filler neck, though. Again, no bubbles just coolant coming up just like if you over filled your sink. I disconnected the main air line off of the compressor and it still did it. It sure doesn't act like a head gasket, I've had those go out before. I really have no ideas on this one. It is in a 389 glider. The water always stays within the normal operating temperature, it has never overheated and the heater will cook you out as you go down the road. Ideas?
     
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  2. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    romulus,mi
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    Water pump impeller is slipping on the gear.
     
  3. KittyKicker

    KittyKicker Light Load Member

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    Dec 27, 2015
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    How would I go about checking that?
     
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  4. starmac

    starmac Road Train Member

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    Fairbanks Ak
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    Simplest things first, make sure your cap is holding pressure. I had a 97 start that and it was just the radiator cap on the tank.
     
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  5. KittyKicker

    KittyKicker Light Load Member

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    I checked that and it is.
     
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  6. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    romulus,mi
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    Unfortunately the only correct way is to remove it.
     
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  7. KittyKicker

    KittyKicker Light Load Member

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    But how would that cause the system to push coolant as the truck is going down the road? If the pump isn't working properly wouldn't the truck overheat?
     
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  8. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    romulus,mi
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    I should have asked this before (my mistake) What is your engine temperature (1) at idle (2) cruising down the interstate?
     
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  9. KittyKicker

    KittyKicker Light Load Member

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    Dec 27, 2015
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    Driver says temps are normal. I drove the truck today and going down the road the gauge hits 185, stays there for about 15 seconds, drops down to 165, stays for a couple seconds then goes back to 185. It just keeps repeating that cycle.
     
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  10. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    Jun 14, 2009
    romulus,mi
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    I don't understand. Is the cycle, 165-185-165 etc., happening while cruising? What is engine temperature while idling and "no heat" issue is happening?
     
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