Need help with overheating issue on my 77 k10 with sbc 350

Discussion in 'Tech Discussion' started by Lens77chevy, May 13, 2018.

  1. Lens77chevy

    Lens77chevy Junior Member

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    I've replaced tstat water pump temp sensor temp gauge upper radiator hose bleed air out of system and it still runs very hot and also replaced radiator cap too I don't have a clutch fan so my fan runs all the time I cant figure out why I'm still running hot I flushed radiator water ran through clear. I'm at a loss any suggestions would be greatly appreciated thanks
     
    Last edited: May 13, 2018
  2. 77 K20

    77 K20 Full Access Member

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    Running hot when? When driving up a long hill? When towing? When just idling?

    Mine started "running hot" when idling or driving at low speeds. If I popped it into neutral and revved it up it would then cool off. In my case it was a bad head gasket.

    There are test strips you can dip into your coolant to see if there is evidence of exhaust bubbling thru it. Or have it idle with the radiator cap off and look for bubbles.
     
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  3. Charlie

    Charlie Full Access Member

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    :welcome:
     
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  4. Shorty81

    Shorty81 Junior Member

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    Are you using a shroud? I have a direct drive fan with a extension to position the fan as close to the radiator as possible. I use a 180 tstat and runs cool.
     
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  5. Obwonkonobe

    Obwonkonobe Full Access Member

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    I always put my sender in the manifold btw, and use a ir gun to double check the temp
     
  6. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Like it was touched on here, you need to verify your temp at the head where the sender is with an IR gauge. The combustion gas test with strips or with the solution and tester they have at the auto parts store would be worth doing.
     
  7. Rusty Nail

    Rusty Nail Build the wall - deport them all!

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    Fan installed backwards?
    Upside down?
    Inside out?

    Ah!
    Radiator hose collapsing on itself mebbe? Does it gots a sprang in it?

    Your flow is all jacked up somewhere ol boy. You ain't got none.

    None.Flow.
     
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  8. Blue Ox

    Blue Ox Full Access Member

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    Here we go again. How much original stuff is left on this thing? You know, that surplus junk the factory puts on, like fan shrouds.
     
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  9. Rusty Nail

    Rusty Nail Build the wall - deport them all!

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    :rape:
     
  10. roundhouse

    roundhouse Full Access Member

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    Usually if t runs hot while sitting still or driving slow it’s an airflow issue

    Radatior , shroud or fan or possibly hot air being able to be short circuited back across the rad , because the rad and shroud isn’t sealed air tight to the core support and the hot air is coming right back around into the front of the rad again

    If it runs hot while driving at highway speed it’s not an airflow problem side you got 70 mpg air over the radatior and engine , highway speed is a water flow problem

    Collapsed hose , clogged rad , etc
     
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  11. Lens77chevy

    Lens77chevy Junior Member

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    Well I used a block tester and fluid did not change so head gasket should be good, I had already ran that test but forgot to put in original post. I have a fan shroud. It runs hot all the time my gauge used to peg hot right away but after replacing tatar and water pump gauge slowly gets hot and it seems to stay between 3rd hash and just before where the red starts. I'm thinking its my rad cause all my horses are good I have no leaks
     
  12. roundhouse

    roundhouse Full Access Member

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    You checked it with the laser thermometer ?

    Or another gauge in the other head port ?
    Or in the upper rad hose ?

    Does it run hot sitting still ?
    Or
    While driving down the road ?

    Sitting still is an airflow problem
    Fan not moving enough air across rad , due to fan or shroud issues

    Get some duct tape and seal up all the gaps between the shroud and rad
    And also between the rad and core support
    And tape some foam strips on top of the core support so when you close the hood no air can travel between the top of the core and hood

    After that’s done you should be able to hold your hand in front of the grille and feel the air moving

    Hold up a plastic grocery bag or some tissue paper and or should stick to the grill

    If it does not , you’re not moving enough air
     
  13. 4WDKC

    4WDKC Full Access Member

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    tstat? just because they are new doesn't mean they are always good or the right temp.
     
  14. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Yeah, I’d verify temp with a laser thermometer, maybe boil the thermostat if you have a kitchen thermometer to verify it, and if you’re concerned about a blockage, you can tee in a flush kit and back flush the system with a garden hose.
     
  15. Crispy

    Crispy Full Access Member

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    I had a similar issue when I replaced the head gasket. Turns out my brand new Stant thermostat was NFG. First time in my life its happened. Ended up buying and boiling a new one to verify opening. Once it checked out I installed it and havent had an issue. This is no knock against Stant, I've never had an issue running their caps or thermostats until this last one.

    Can you elaborate on your fan set up? I would start looking their before tearing into the engine again.
     

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