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Hello. I have a Zodiac 601 HDS with a 100HP 912ULS. The airplane was built in 2000 with a VW radiator hanging under the fuselage as the Coolant radiator. It works well. The coolant temperature is usually 180F, and on very hot days it may go to 190F. I want to replace the VW radiator with a Rotax radiator inside the cowling, with the hope that there will be less drag. Since my coolant temp does not at present go over 190F that leaves a bit of room for a coolant temp increase in case the inside the cowling Rotax radiator does not work as well as the large outside VW radiator.
My concern is the oil temperature. It is sometimes close to being high on very hot days. If replacing my coolant radiator does raise the coolant temp by 20, 30 or more degrees, will that cause a rise in the oil temperature? Thanks.
  • Re: Rotax Coolant Radiator

    by » 7 years ago


    Possibly a tad. Oil temps usually run around 190F - 225F. It could go up to 230F - 245F on a hot day in climb, but should come down in cruise. Coolant temps many times are about 10F-20F lower than oil temps, but each plane is different depending on how the coolers are set up and mounted. Seeing a coolant temp between 190F & 220F I would say is fairly normal. Flying in cold country during the winter of course will cool these down.
    My coolers are stacked back to back in my plane. I live in Tucson, AZ and in the hot summer my oil temps would run around 218-220F and the coolant would run around 205F at 5200 rpm in cruise. There also may be a 10F+/- spread in left to right cooling temps. On a hot day my climb oil temp would be 230F and maybe 235F, but once leveled off would come right down.

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


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