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Oil leak from a through bolt.

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Oil leak from a through bolt.

Postby Clive » Wed Jul 31, 2019 12:21 am

Hi folks, it’s been a while since I had a Jab problem but I find myself with a pesky oil leak from one maybe two through bolts.
The cause I believe is break through from the oil gallery adjacent to the associated through bolt.
Now when I replaced the through bolts after a breakage a few years ago I found one gooped up with silicone sealant.
I though ah, here we are, this engine must have has a through bolt leak in the past. I’ve always had the engine and knowing it’s history the goop must have been put on either by our friends in Bundaberg or by ST aviation at the 1000hr overhaul.
Any how, no matter who or when. I re gooped the new bolt in the previously gooped hole and all was well.
Recently though I have isolated the oil leakage to at least one of the bolts on the lower side of #3 cylinder.
Strangely the bolt that I seem to remember being the one that snapped.
This would fit with the theory of the use of engines in the training environment which is what promoted the broken bolt some years. Back when my son and son in law started to learn to fly in my (now our) aircraft.
My question is does anyone have any tips on gooping a through bolt?
I plan to do what I did last time which seemed to work as the previously gooped one hasn’t leaked.
I ask this as it a few years down the road now and maybe others have come across and fixed through bolt leaks?
BTW this is an early 2200 with 1700 hours in it. Treated with great TLC until flown under guidance from a flying instructor.
Thankfully it will now be flown once again with TLC as the licence has been received.
Regards to all, Clive
Jabiru SP with 2200 @ 1700 Hours
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Re: Oil leak from a through bolt.

Postby diablo » Sat Aug 10, 2019 5:57 am

Hi Clive,

I presume that it is not one of the bolts that goes straight through the crankcase but one of the studs. It sounds like there is some sort of wear, warp or crack internally, possibly the thread that you found filled with silicone ... I really don't think it came out of the factory like that.

Cracks in places like that are unusual. Best to go back to basics which probably means a complete strip down and identification of root cause. Anything less, is just a patch on what seems to be a bigger issue. If it is a crack, a good engineering outfit will be able to stitch it and machine the mating surfaces to spec.

Happy to help out on the strip down and catch up. I also have a guide on stripping top and bottom half (in colour) if you need one.
Sent from my "Electronic Numerical Integrator And Calculator" E-N-I-A-C
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