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Thread: High Oil Temperature

  1. #1

    High Oil Temperature

    So after 11 years and ~840 hrs of flying my oil temperature is going crazy. It measures ~ambient temperature at start and then as the engine warms so does the oil - ok that's normal but the temperature just keeps going up and the last couple of flights it's gone off-scale high (160+degC). All other sensors, i.e. oil pressure, EGTs, CHTs, etc, remain normal. Reviewing the data from the AF3500EM I see the temps did start trending up late last year, but nothing like what they are now

    My last task before shutting the engine down is a mag. check, and before that I shut everything else down with the alternator being the last item turned off. At the end of my last two flights I've noticed that when I turning the alternator off the oil temperature returns to normal, which makes me think I have an alternator problem however an avionics engineer has suggested it's more likely to be an oil temp. sensor problem than the alternator.

    We've tested the oil system and everything's fine there, ditto the temp. sensor and vernatherm have been tested and we believe are operating normally.

    Other posts on this forum imply I should replace the sensor with a 2-wire model, and also that what I have may be a standard automotive sensor (it came with the sensor pack I purchased in 2007 if that helps).

    I'm happy to replace the sensor, but then I'd need calibration numbers etc

    Your thoughts and guidance would be appreciated

    RV7QB ZK-NVS/AF3500EF & EM/GNS430W/SL30/GTX335/TT ADIP II - 840 hours (Hobbs)

  2. #2
    The most usual cause of a high or jumpy oil temp reading is that you have a bad engine ground. The fact that the reading goes back to normal when you turn off your alternator strongly suggests this is the case here as well. To further test the theory, try turning on and off large electrical loads (landing lights, pitot heat), does the oil temp jump further? Then, if you are comfortable, try shutting off the alternator in flight for a few seconds. Do the temps return to normal as they do on the ground? It should only be necessary to try a two wire oil temp in the event you are unable to fix whatever is loose and/or corroded in your engine ground.

  3. #3
    Thanks Jonathon, will do

    RV7QB ZK-NVS/AF3500EF & EM/GNS430W/SL30/GTX335/TT ADIP II - 840 hours (Hobbs)

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