"Ticking" Jabiru 3300?

·         John Austin

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I've had 340+ trouble-free hours with my Jab 3300 (#2427) in my Zenith STOL CH750. No problem with CHT's, EGT's, routine oil changes about every 25 hours, and oil analysis always say "your metal wear levels are much lower than average for Jabiru 3300's!"

However, I've had an odd thing occur a couple of times in the last 6 months ... Twice, after 2-3 hour cross-country flights, I've taxied-up to a ramp and shut down and someone observing walks over and says, "What's causing that ticking sound your engine is making?" Both times, all engine parameters were normal, especially obvious things such as oil pressure. My hearing isn't the best and I wear a Bose ANR headset, so I've never heard the "ticking." Lately, I've even tried removing the headset while idling the engine prior to shut-down, but I haven't heard a thing. I guess it is possible it could have happened more than twice ... it's not always the case that someone is standing and listening close-by when I shut-down!

What do you suppose causes the "ticking" and is it harmful?

John
N750A

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John
N750A
Zenith STOL CH750, Jabiru 3300

·         Doug Smith

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Hi John,
Sounds like you've got the preventative maintenance and monitoring well in hand, glad to hear it's going well.
Unfortunately I don't know of a "standard" answer for a ticking engine; I'd suggest that the valvetrain would be the place to start looking - possibly a lazy lifter would fit your description. But having said that I know several cases where engines that tended to tick and it was just a benign characteristic of the engine and didn't ever cause an issue. I will ask around and see if there's anything else worth your checking in to. There are no other symptoms I take it? No rough running, uneven idle etc?
Best Regards,
Doug.

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·         John Austin

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Doug Smith wrote: Hi John,
Sounds like you've got the preventative maintenance and monitoring well in hand, glad to hear it's going well.
Unfortunately I don't know of a "standard" answer for a ticking engine; I'd suggest that the valvetrain would be the place to start looking - possibly a lazy lifter would fit your description. But having said that I know several cases where engines that tended to tick and it was just a benign characteristic of the engine and didn't ever cause an issue. I will ask around and see if there's anything else worth your checking in to. There are no other symptoms I take it? No rough running, uneven idle etc?
Best Regards,
Doug.

No other symptoms at all - it'll idle smoothly down to about 600 rpm! Did a recent dynamic prop balance and got the engine/prop down to 0.015 ips @ 2850! (Doesn't get much smoother than that!) As I said, it has only been noted by observers twice and those two times were nearly 6 months apart, but both were co-incidentally (or not?) after 2-3 hr cross-countries whereas my typical flights are about an hour. But, like I said, it could also have happened and either I didn't hear it or there was no one near the plane to hear it prior to shut-down. Just completed annual recently - all cylinders with excellent compression on leak-down test and found nothing amiss with a visual inspection under the tappet covers.
John

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John
N750A
Zenith STOL CH750, Jabiru 3300

·         Doug Smith

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believe it or not, sometimes when you park near a shed or concrete certain frequencies of the engine reflect differently and it can sound quite different. There's an area behind Jabiru where, if you listen to the engine from a few metres away, all you can hear is the timing gearbox whine reflecting off the hangar next door. It could be something like that, especially if there are no other symptoms.
If it happens again and you're in a safe spot you could try doing some run-ups and see if the noise stays there at increased RPM / oil pressure etc, just out of curiosity.
Regards,
Doug

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·         Quentinb

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I notice that ticking sound on my 3300. It sounds to me like dissimilar metals cooling, kind of like a metal framed house warming up or cooling down?

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·         Doug Smith

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Hi Quentin,
Ticking after shut down is normal enough - particularly from the exhaust as thermal stresses sort themselves out. Or did you mean you can hear noises like that while the engine is running?
D.

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·         Quentinb

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After shutdown