CHT temperature

My plane has 0470M engines with the Bendix PSD-5C pressure carbs. I only have a single thermistor probe cylinder 3 each engine. While both engine indications of EGT and CHT have matched after start climb cruise the left engine CHT temperature still matches until I lean in cruise. At that point the CHT drops to about 225 . If I push its mixture control to full rich it then mirrors the right . The thermistor probe checks good and gauge has been overhauled. Any ideas what could be causing this change in cruise?

Comments

  • Scott ShererScott Sherer COO Forum Moderator

    I will send this to our A&P, Erich Rempert for his comments. Please stand by.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Scott ShererScott Sherer COO Forum Moderator

    Here are comments from Erich:

    The only thing I can think of is #3 cylinder on the Left engine has an induction leak and is running leaner than the others when you reduce power. (So lean; the temp falls off because it's not making power anymore).

    What happens to the EGT?

    Go over all the induction clamps and couplings closely. Also possibly look for a broken primer line to #3 cylinder.

    Since things match up at full power/full rich and present after leaning for cruise it sounds like an induction leak based on what you've given me.

    [Induction/Vacuum leaks become more apparent at lower manifold pressures, at full throttle their effects virtually disappear because the manifold pressure is almost the same as atmospheric.]

    An engine monitor would give us a much larger picture of what's happening and be very helpful in this instance. As of now we don't know if this is a problem effecting one cylinder or the whole engine.

    You also didn't mention if the EGT probe is also on #3, if it isn't, it's indications are of little value when diagnosing this issue.

    ~Erich Rempert, IA Consultant

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

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