Vanishing coolant help

Discussion in 'Engine Topic' started by Coastie, Jun 10, 2018.

  1. Coastie

    Coastie New Member

    Jun 10, 2018
    So I've got a 79 trans am with a 400, I know I know, not a Camaro, but I figured y'all could help.

    I have coolant magically vanishing, but not completely.

    I can fill the radiator up to the top, turn on the car, and watch the coolant level drop 4 inches in seconds with a steady stream of bubbles until it reaches a certain level, and then stops. I can drive the car all day like that and no more coolant vanishes.

    Doesnt over heat, runs great, no smoke, no smell, oil and coolant are regular coolers, no leaks that I can find. My overflow bottle is dry as well. Any idea what is causing this? I hope it's not a head gasket on worse, but it doesn't show any of the other symptoms. You'd figure with half a gallon of liquid disappearing in 10 or so seconds, there would be some smoke or something.

  2. budro6968

    budro6968 Veteran Member

    Apr 2, 2016
    Jax Florida
    How long does the car sit between start ups? Do you have to put that much in every time? If you can't see a leak and it is not getting in the oil pan like making your oil milk shake color. I don't know what to tell you. My old Chevy Truck sits for weeks and I have to add at start up. I think it is a freeze plug on the back of the engine. Has a very slight leak. I don't see it while running but when it sits I see rust spots on the ground. I'm going to have to break down and pull the trans to get at it. B/C when it goes it won't be pretty.
  3. Coastie

    Coastie New Member

    Jun 10, 2018
    I daily the thing, and I only noticed it a few days ago. Sometimes I have to add half a gallon, other times just a cup. Just did it today and the level isn't going down anymore
  4. NotUniqueEnough

    NotUniqueEnough Veteran Member Lifetime Gold Member

    Feb 25, 2007
    Have you pressure checked it? Maybe it was a pocket of air that has finally worked its way out?
  5. Coastie

    Coastie New Member

    Jun 10, 2018
    I'm starting to hope it's that
  6. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

    Jun 11, 2002
    Northern VA
    When you fill, do you also fill the overflow tank to at least the "Cold" mark? If not, you may be sucking in air.

    I had a radiator with a pinhole leak, could never see the leak, but could smell coolant under the hood after a drive. Finally swapped the radiator on a whim, no more issue. Then a year later it started again... found the rear intake bolt loose on the passenger side, was weeping out the back- not enough to pool, just enough drop the level slowly over time.
  7. Rich Schmidt

    Rich Schmidt Veteran Member

    Mar 27, 2010
    Denville NJ
    It sounds normal. Chances are a small portion of your upper radiator hose or heater hoses are located higher than the radiator cap. Start the engine cold and top off the radiator with the engine running and put the cap on,then fill the overflow to the proper level.
  8. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

    Oct 2, 2013
    I'm thinking the system was never burped properly, and with the overflow not being filled, just kept adding to the problem. I think eventually, it may have worked itself to the right level. If you don't see coolant leaking, even in the oil, and don't smell it burning on the block someplace, then you should be ok. Just fill up your overflow and drive.
  9. 1980RS

    1980RS Veteran Member

    Jun 17, 2006
    Bubbles in the cooling system is usually a sign of a bad head gasket. There is something you can buy, you put fluid in it then put it at the radiator cap opening, then if the fluid changes color, you have a bad head gasket or something like that. We used to use it all the time back in the 80's at work.

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