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Intermittent "low coolant" light........

Discussion in '1982-Present GM Diesel' started by Can Can, Apr 1, 2004.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Intermittent \"low coolant\" light........

    My "low coolant" idiot light has been flashing on and off intermittently for the last few weeks. The rad is full so I'm not quite sure why it's happening.

    The wierd part about it is that it seems to flash only when I'm going downhill on very slight grades at highway speeds. It will only flash for a second or two and then go out. Tonight I drove 120 miles round trip and it flashed about 4 times for no apparent reason....... Temp gauge was reading normal at the time./forums/images/graemlins/dunno.gif
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Intermittent \"low coolant\" light........

    Bad sensor? I can't think of what else it could be if the coolant isn't low.

    Rene
     
  3. imiceman44

    imiceman44 1 ton status

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    Re: Intermittent \"low coolant\" light........

    [ QUOTE ]
    Bad sensor? I can't think of what else it could be if the coolant isn't low.

    Rene

    [/ QUOTE ]

    Or a loose wire grounding on something.
    /forums/images/graemlins/doah.gif
     
  4. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Re: Intermittent \"low coolant\" light........

    Check on the passenger side of the rad. Should be easy to see. Mine was solid on and I pluged it back in and it was fine.
     
  5. JeffHK5

    JeffHK5 1/2 ton status

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    Old ars post

    Yep , I know it's a "older than dirt" post but mine has started doing the same thing!

    Canmore, what was the fix?

    Thanks, Jeff
     
  6. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Wow, I was surprised to see this post up at the top........:rotfl:

    I'm *pretty* sure that the "low coolant" light is being caused by air in the system, either through a bad head gasket/cracked head or a bad/cavitating water pump. Since then I have had some wierd cooling issues, as well some intermittent boilover into the coolant reserve tank.

    Regardless, I've put another 20K on the 83 with all this happening, and it's still running fine. The reason I'm not worried is because the truck has been relegated to farm duty status, and doesn't see much road time anymore. One of these days I'll probably end up trying to see if I can solve the issue, but until then I have better things to spend my time on.

    Sorry I couldn't offer you any solid conclusions, brother. Are you having similar issues, by any chance?
     
  7. JeffHK5

    JeffHK5 1/2 ton status

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    No boiling over but it does have a strange working thermostat, it will go up to 230 degrees before it opens for the first time. The coolant light will come on at all different temps and RPMs , no pattern.

    Is the sensor in the overflow tank , where it actually measures fluid level or is an idiot light that works off a temp. sending unit?

    I was thinking that a bad temp. sender could give me the impression that the thermostat was opening at 230 and would make the "low coolant" light come on and go off randomly.

    I like the old 6.2 but these phantom cooling problems are a little frustrating!

    Jeff
     
  8. jarheadk5

    jarheadk5 1/2 ton status

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    I'll scan the relevant pages out of my book and post 'em up tomorrow. Might help both of you...

    ***EDIT***

    Scanned and posted in the "6.2 Tech Info" sticky post. Hope it helps...
     
    Last edited: Aug 9, 2006
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'm doing the head gaskets and water pump on Paul's old truck right now. FWIW, there were no signs of cavitation with the old pump and no 'smoking gun' with the head gaskets either. Looks like number two cylinder was where the problem was though. That piston is very clean, and that exhaust port on the manifold is the only one with rust spots...

    I've never had the coolant light come on with this truck though.

    Rene
     

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