Why is my 800GS squirting coolant fluid UP at me?

Discussion in 'Parallel Universe' started by GB, Aug 18, 2010.

  1. Pyranha7

    Pyranha7 Shiny Side Up, Right?

    Joined:
    Aug 13, 2008
    Oddometer:
    15
    Location:
    Lakewood, CO, USA
    I had the same issue with coolant spewing out. In my case, the radiator cap was faulty. The radiator would push excess into the overflow but could not pull it back in. So the coolant was coming from the overflow once it filled up. Dealer replaced the cap with no hesitation.
    #41
  2. Steveman

    Steveman Been here awhile

    Joined:
    Sep 14, 2011
    Oddometer:
    475
    Location:
    Austria
    +1 This is the first technically correct explanation in this thread.


    If your bike does this constantly something is wrong, and this could be the answer:

    For those not so familiar with the function of the systems a few words and pictures which may help you understand how it works.
    I often have been asked how it is possible that in a closed pressurized cooling system the overflow can (or better expansion tank) has just a simple hole to release excess water/fluid. The question itself shows that there is a misunderstanding how the radiator overpressure valve works. In fact this valve sits in or on the cap. The valve with its sealing rubber closes the radiator pressure tight. The lid just holds the valve in place. Most people think the lid is what closes the radiator pressure tight but it is just there to hold the valve in place. When you install it you need to push it down a little which gives the valve the preload.
    In fact the radiator cap contains the valve(s) like you can see here:

    [​IMG]



    The overflow tube, where the hose to the expansion tank is connected sits exactly in the center between the valve closing the radiator and the lid holding the cap/valve in place, you can see it here quite well.


    [​IMG]


    The radiator cap contains two (!) valves, a pressure relief valve and - less known - a vacuum valve. When the water or cooling fluid gets hot and expands the pressure reliev valve holds the rad tight until the maximum pressure is exceeded. If everything is right, this should not happen, but if it happens the valve opens and releases fluid into the expansion reservoir. And from there it can under certain circumstances be blown through the small hole in the cap. The moment you get the stuff right in your face as described...

    When the cooling liquid or water cools down after you turned your engine off the valve in the cap opens in the other direction to avoid a vacuum. When this happens the vacuum sucks water or cooling fluid from the expansion tank back into the radiator and the pressure between radiator and expansion tank is even (ambient pressure). Unfortunately there are serveral circumstances leading to malfunction. First and most known problem is a defective rad cap, meaning the pressure valve in the cap opens to early. This reduces the boiling point of both water or cooling liquid and may result in overheat, steam coming out of your expansion tank. Simply replace cap, done.

    Less known is that the vacuum valve in the cap can also fail meaning that when your engine cools down after shutting down the vacuum can not be released. Result is that your cooling hoses look like they were squished. This malfunction can also lead to overheat as whenever your system is very hot cooling fluid is pressed into the expansion tank but it will never be sucked back. And finally there is not enough cooling fluid in your radiator.

    An easy method to check if the vacuum valve works: take the cap off, squash the lower hose on the rad with your fingers as much as you can (a little bit of water may flow out when you press), put on the cap again and then release the hose. The hose should immediately jump back into its normal shape.


    So what is the reason that the described problem appears sometimes when riding in higher altitudes but everything is normal when riding between zero and 5000 ft?
    Mainly it is air in your system which is not really a big problem on sea level except it is very much air. The air in your system will expand due to the heat and even more due to the altitude, a physical property. When there is water or cooling fluid in the expansion tank and it is at maximum or even more as soon as the pressure relief valve in the cap opens the described effect will appear and you may get a mouth full of (hopefully) water in your mug :)

    This is simply as there is not enough room in the little catch tank and imagine fluid is pressed with about 15 psi through the tiny hole.... it will squirt like crazy....
    To avoid getting all the fluid in the face you could try to use a cap like shwon below and install a hose. But check that the fluid can not reach your rear tire or brakes.


    [​IMG]


    If you think the pressure reliev valve opens only if the fluid is too hot you are wrong. Even if the temperature is within limits pressure may be released, for instance when there is a lot of air in the system. In high altitudes water and cooling fluid and most other fluids will boil earlier. The higher you go, the lower the boiling point will be. And the fluid will expand more than on sea level.


    Why does it even happen when fluid levels are OK and the rad cap with the darn valves is new?
    Mh...well, it has to do with the design and it is not a poor design as it happens with all liquid cooled bikes. Once your bike is running hot due to high ambient temperatures and traffic riding or both it will press some fluid into the expansion tank (a while before the fluid starts cooking!!). Maybe only a few drops. After cooling down you will have a vacuum in the system. And the vacuum valve will open and will suck fluid back. And exactly here we have a problem as in the radiator neck 5 out of 10 times there is a little bit of air which is when the radiator vacuum valve opens sucked into the radiator. Or just the fluid in the resrvoir contains little air bubbles which are sucked back in the radiator.....

    This is no problem under normal operations as these systems to a ceratin degree are able to bleed themselves...but in high altitudes all the negative factors add.

    water/cooling fluid boils earlier
    engine temperature is generally higher (thin air less cooling effect plus above mentioned item)
    you may ride slower - less cooling effect
    system pressure is higher than on sea level
    air in the system will expand much more than on sea level....

    Apologise for any grammar and spelling errors.


    Cheers
    Steve
    #42
  3. lmclamore

    lmclamore Citation Collector

    Joined:
    Jul 9, 2010
    Oddometer:
    412
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    Washington DC area
    That is an excellent explanation Steveman. Thank you very much for taking the time. Now I get it.
    #43
  4. Steveman

    Steveman Been here awhile

    Joined:
    Sep 14, 2011
    Oddometer:
    475
    Location:
    Austria
    Thank you, my pleasure! :1drink
    #44
  5. seaswood

    seaswood seaswood

    Joined:
    Nov 7, 2008
    Oddometer:
    825
    Location:
    Ocean motion
    Yeah, the bleed screw is the upper left screw on the water pump. It helps to "massage" the water hoses.

    Anyone have know where there are photos/diagrams of the bleed screw & where to drain system?:eek1
    #45