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  • Re: Low Coolant Level

    by » 11 years ago


    Not all cooling systems exchange coolant between the fill tank and the reservoir. If the system runs a little cool it won't exchange coolant like a system that runs hot. The fill tank is at the high point on the coolant system and if the coolant is at the top when the cap is off there is no way to get air into the system. Air rises and doesn't sink to get lower. The air will always seek the high point as coolant moves through the system. If the engine has been running and was full then I doubt air is in the system that has not moved. I have done 30 plus hose changes this last year and all I do is fill the coolant tank until it tops off then the reservoir. Not a single one has needed additional coolant after running, nor has there been any coolant loss in the main system after test flights. If the system was full to start with and was full after several runs then I guarantee you have a leak. If you can't see it, then when the system builds pressure in flight the air flow over the engine is blowing it off.

    If you are loosing coolant you need to find the leak. That is the only way to loose coolant in a small volume closed system. Coolant has to be going some place. If it was full it can't have 400ml of air in the system. 500ml is 17 oz (2 cups) of fluid in a system that usually only holds 2/3 gal. That's a lot to loose.


    (Unless you have an odd system that has the radiator or hoses higher than the rest of the engine)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Low Coolant Level

    by » 11 years ago


    Thank you all for all the advice and help. The cooling "loss" occured after I had drained and refilled the coolant during a 100 hour inspection and it is very clear now that it was air in the sysytem that was the problem. I've flown about 10 hours since with no further coolant loss and, aftrer hard looking, no evidence of a leak.

  • Re: Low Coolant Level

    by » 11 years ago


    Hi Joseph,

    "The cooling "loss" occurred after I had drained and refilled the coolant during a 100 hour inspection and it is very clear now that it was air in the system that was the problem."

    That part would have been a good to know. :lol:

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Low Coolant Level

    by » 11 years ago


    If you empty the coolant and refill the system, no matter how slowly you pour the coolant in I guarantee you will get air pockets and the coolant will need to be topped up after the initial warm up. If the coolant isn't topped up, and there is air trapped, it could lead to hot spots within the cylinder head.

    Mark

  • Re: Low Coolant Level

    by » 11 years ago


    Interesting that the Rotax Line Maintaince procedures for coolant replacement make no mention of this problem, especially if it can lead to head damage. I guess that is why I did not consider the replacement as the source of the problem until it was pointed out here: A very good reason for this forum.

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