no coolant in overflow tank. bad?

Posted by AlphaAssault, Sep 14, 2008

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  1. AlphaAssault

    AlphaAssault Proven Member

    Joined Sep 5, 2007
    Tyler, Texas
    i was recently checking all the fluids in my car, and i noticed that the coolant overflow was completely empty WTF. i dont remember the last time i filled it up, but i do know there is a low-coolant light by the gauges, and i thought that would alert me when the coolant got low. well, i pulled the overflow container, and found that the sensor plug at the bottom of it wasnt plugged in all the way. i checked the overflow bottle for leaks, then put it back in the car and filled it to spec. then i checked under the radiator cap, and there was plenty of coolant there. if it helps, i checked the oil for coolant, and coolant for oil with the idea in mind that maybe a bad head gasket is at fault for emptying all the coolant, but both oil and coolant were clean. could i have done any damage by running without any fluid in the overflow container? i dont know how long i was driving with it empty, but the temp gauge never got above the middle mark. ideas?

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  2. EvansF

    EvansF Proven Member

    Joined Feb 9, 2008
    if you checked the coolant by the radiator cap and it was full, you are fine. Maybe you are burning coolant, and yeah it can be a bad head gasket. Look at you're exaust to see if it's smoking white, it will tell you if you are burning coolant.
  3. AlphaAssault

    AlphaAssault Proven Member

    Joined Sep 5, 2007
    Tyler, Texas
    my car has never had smoke of any color come out of the exhaust.
  4. knochgoon24

    knochgoon24 DSM Wiseman

    Joined Jan 29, 2008
    Troy, Michigan
    Just top it off and you're good to go as long as you aren't having any other problems.
  5. xdxoxuxgx

    xdxoxuxgx Proven Member

    Joined Sep 25, 2006
    Gilbertsville, Pennsylvania
    When I put my FMIC kit on, I removed my coolant overflow bottle. I don't know if that's bad or not, but I check my fluid levels regularly so I don't worry about it.
    My DSM:
  6. AlphaAssault

    AlphaAssault Proven Member

    Joined Sep 5, 2007
    Tyler, Texas
    which begs the question: if our cars run fine without the overflow tank, why is it even there? i didnt notice anything while driving that would lead me to believe that the overflow bottle was empty. and had been empty for a while. is an overflow bottle more important to a healthy engine or to a not-so-healthy one?
  7. gregalmighty

    gregalmighty Proven Member

    Joined Mar 22, 2008
    Sheffield Lake, Ohio
    As long as the car isn't overheating or running hot and there is still coolant in the system then you haven't hurt anything. Have a friend drive behind you and watch for smoke. A lot of times you can't see it in your mirrors. If its mysteriously disappearing and theres no signs of a leak under your car where you park then thats probably the case.
  8. jumpfroggy

    jumpfroggy Proven Member

    Joined Dec 1, 2005
    Jamestown, Rhode Island
    The coolant oveflow tank is for overflow. AFAIK (maybe someone will correct me on this), the coolant system pressurizes during engine use. The radiator cap maintains pressure by leaking a bit out if it gets too much. This extra goes into the overflow tank. Once the engine is turned off and cools off, the coolant system depressurizes and can sometimes suck some coolant back in.

    If you take the coolant out of an overflow tank for a perfectly working cooling system with enough fluid, you probably wont have any problems. However, it can be a warning sign of other things. Basically, you probably have no problem since the fluid levels are fine, but you want to make sure the overflow tank is half-full. That way you can tell if there's too much pressure (too much coolant in the tank), or if there's a coolant leak somewhere (tank keeps going empty).

    But I'm sure if you kept on top of the coolant levels, you could basically run without an overflow tank. And why did they put one in in the first place? Can't have all your manufactured cars spitting coolant out onto the street whenever they feel like it. What an environmental (and PR) disaster.
  9. Defiant

    Defiant DSM Wiseman

    Joined Jan 13, 2003
    glorious Galt, California
    It's an expansion tank. Modern cars don't run a void in the top of the radiator, they run a cooling system with no air space. The coolant heats up, expands into the tank, and sucks back as it cools.
    Do not try to run a street car without one.
    My DSM:
  10. vanilla gorilla

    vanilla gorilla Proven Member

    Joined Sep 11, 2007
    Orrum, North Carolina
    As everyone else said, you are fine. Just keep an eye on your coolant level. I ran my car for a long time without an overflow, I just keep a check on the coolant.
  11. 99gst_racer

    99gst_racer Moderator

    Joined Apr 5, 2003
    Coloma, Michigan
    Defiant is 100% correct.

    Just because it's empty, doesn't necessarily mean something is wrong. It's normal operation includes filling and emptying itself. And yes, do not drive without one, or you will eventually have a low coolant level.
    My DSM:

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