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  • Re: New 582 shortblock overheating

    by » 10 years ago


    Hi Peter,

    Food for thought:

    Here are some thoughts on coolant mixtures.
    You are correct that the more water the more heat transfer capability, but that comes at a price.
    It is recommended to never go below a 40% coolant and 60% water mix.
    If you have a 40% coolant and 60% water your temps range is -60F to 270F for boil over.
    If you have a 50/50 mix then the temp range is -34 to 265F
    If you have a 25% coolant and 75% water the the range is 10F to 255F.
    Anything past 75% doesn't have any real effect anymore. You loose a lot of boil over protection by being at 20/80 and you could realize that situation fairly easy inside your engine. You can develop hot spots that won't show on the water temp gauge and these become vapor spots and then they have no cooling at all and then metal fatigue sets in. You also start to loose your corrosion protection.

    I know we are talking about your 582, but the theory is still sound.
    These numbers and isolated vapor spots is the exact reason Rotax recommended for the 912 only a 248F max coolant temp with the 50/50 mix. To get higher you need to use Evans waterless coolant, but that comes with a 25F-30F higher temp penalty across the board unless your engine is fully exposed to open air. Tightly cowled engines don't tend to do well with Evans as the temps may sometimes soar above the max because of the poorer heat transfer of Evans. Evans has a 370F boil point, but doesn't transfer the heat out as well because it has no water.

    There are other ways to cool your engine you may to consider. (i.e. a little richer fuel mixture, reposition of the radiator, a larger radiator, relocation of the radiator, ect...)

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


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