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HIGH CHT NORMAL EGT & OIL TEMP

in 912 / 914 Technical Questions 7 years ago
My 912ULS (SN 5644349) with 368TT is installed in a 2005 Rans S-6S. Over the past year I have been experiencing high CHT on cylinders #1 & #3 but primarily #3 intermittently. The CHT will sometimes stay in the normal range and sometimes rise to 275f within 5 minutes from cold start. When high the EGT and oil temp remain normal. Suspecting my CHT sensors I've used a digital temp meter focused on the sensors and received approximately the same temperature. To date I've flushed the system and refilled with Dexcool 50/50, replaced the lower coolant hoses and radiator cap. What should I look at next?
Thanks - Mike

  • Re: HIGH CHT NORMAL EGT & OIL TEMP

    by » 7 years ago

    Make sure the connector on the probe is snug and does not move freely. It should have some stiffness when you try and move it. If it is too loose it will be erratic in readings. Check for a loose wire in the connector and it isn't cut or the wire abraded somewhere.

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

      
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  • Re: HIGH CHT NORMAL EGT & OIL TEMP

    by » 7 years ago

    I removed both CHT sensors and cleaned contact areas on sensors and the engine block. With an OAT of 55f the CHTs were both approaching 250f after 5 minutes. My infrared thermometer focused on the sensors read similarly indicating a cooling system problem and not the sensors or EIS.
    Thanks - Mike
      
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  • Re: HIGH CHT NORMAL EGT & OIL TEMP

    by » 7 years ago

    I removed both CHT sensors and cleaned contact areas on sensors and the engine block. With an OAT of 55f the CHTs were both approaching 250f after 5 minutes. My infrared thermometer focused on the sensors read similarly indicating a cooling system problem and not the sensors or EIS.
    Thanks - Mike

    Follow-up: because of the intermittent nature of the high CHT on #3 and having exhausted my limited knowledge otherwise I'm going to start looking for a vacuum leak on the #1-3 bank. Any suggestions as to the usual suspects appreciated.
    Mike
      
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  • Re: HIGH CHT NORMAL EGT & OIL TEMP

    by » 7 years ago

    USE EVANS COOLANT AND TRY TO GIVE GROUND RUN.
    HOPE NEVER FEEL SUCH HIGH CHT.
      
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  • Re: HIGH CHT NORMAL EGT & OIL TEMP

    by » 7 years ago

    Don't use Evans.It isn't recommended anymore and carries with it a 20 - 30F temp penalty. Your 50/50 should be fine and water is by far a better heat medium. Depending on your aircraft it could just be the setup. It could be something like a thermostat, a hose slightly crimped down and not allowing full volume flow, air in the system, radiator needs cleaning inside or out, an oil / coolant heat exchanger (I'm not a fan of them and the temps seem to run higher) and it may just be poor air flow through the cowl especially on the ground vs in flight with forced air flowing through the cowl.

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

    Thank you said by: Capt. Siva,, Michael Nault
      
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