Coolant leaks from reserve tank hose at higher temperatures

Discussion in 'Mechanics Garage' started by IvanGrozni, Oct 2, 2018.

  1. IvanGrozni

    IvanGrozni New Member

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    Hello guys

    The issue:

    When the temperature reaches 104'C my coolant is starting to leak from the reserve tank hose.
    Then the radiator fan starts and cools the engine and the leaking stops.
    Then if the temperature increases the above repeats :(

    There was enough coolant when I checked at the radiator cap.
    I don't remember this happening before...

    Any ideas? Maybe air in the system and the coolant boils?

    (vfr800 Fi 99)
     
  2. OOTV

    OOTV Insider

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    Most likely the radiator cap needs to be replaced. This has happened to me, twice. If the cap doesn’t hold pressure it opens up sending coolant to the overflow reservoir and sometimes it works like a siphon hose, meaning that once it starts flowing out the overflow hose, coolant keeps on flowing as it’s lower than the radiator cap. It also possible your thermostat is stuck but the radiator cap is a quick and easy thing to try. If that doesn’t resolve the issue, then look into the thermostat. That is a much more time consuming venture however.
     
  3. IvanGrozni

    IvanGrozni New Member

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    Thanks a lot for your answer! I agree about the cap part - sounds logical. Will change it.
    But I can't understand how stuck thermostat can be causing this issue. Do you mean if it's stuck close the volume is smaller and the pressure higher or something? The pressure should be the same regardless of the thermostat... Also afaik the thermostat just stops the flow and not isolating the small from the big circuit of the cooling system. Not sure though :)
     
  4. OOTV

    OOTV Insider

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    Typically a stuck thermostat will either mean your bike runs too cool or too hot, the latter condition usually causes your bike to over heat and thus create the flowing of coolant to the overflow reservoir. If your bike seems to run fine, as in warms up and cools down normally, the the radiator cap is more likely the culprit.
     
  5. Diving Pete

    Diving Pete Member

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    Rand following on from the previous posts - very very few people ever change the Rad cap... yet I'm fairly sure it's a service item - lol
     
  6. IvanGrozni

    IvanGrozni New Member

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    New cap - no problem :)
    Btw I bought an automobile part - 7 euro instead of 35, same cap
     
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