912S Reduced Oil Pressure.
in 912iS Technical Questions
14 years ago
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Re: 912S Reduced Oil Pressure.
by Mike Brown » 13 years ago
James,
Don't know what Rotax would recommend, but I would go ahead and tap the housing a little deeper with a 1/8 npt tap. You are going to install some sort of hose barb anyway and a 1/8 npt barb will be the easiest to find. Mike's measurements are correct and tapping should give you a proper clean cut for a 1/8 npt fitting. I have no doubt that Rotax will resolve the mistake for you, but you will grow old waiting for the new parts.
Bill.
I'd be reluctant to do that as the threads are too close in major diameter. The 1/8"-NPT tap will pretty much wipe the M10-1.0 threads and leave you with very shallow pipe threads that won't allow much thread engagement for the 1/8"-NPT temperature sender. Risky business as we're talking about the oil circuit here. Losing the oil pressure sender in flight will dump out all your oil pronto.
First thing I'd do is determine how deep the 1/8"-NPT sender was installed into the M10 threads. Are there undamaged M10 threads below the maximum depth to which the 1/8"-NPT sender was installed? If I could get 4 or 5 mm of clean thread engagement on the M10 sender I might be tempted to clean up the female threads with a M10-1.0 tap and install the M10 sender. Probably with blue Loctite 243.
A refinement on this approach would be to use a M10-1.0 back-tap, which would pull any metal out of the hole instead of depositing it in the oil pump.
The correct fix is of course a new oil pump housing.
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Re: 912S Reduced Oil Pressure.
by bill martin » 13 years ago
James,
Another option might be a helicoil if you have enough metal in the housing to enlarge the hole. You can get fine thread metric tangless m10-1 helicoils fairly easily.
Bill.
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Re: 912S Reduced Oil Pressure.
by Mike Brown » 13 years ago
I like Time-Serts. A solid insert and a truly permanent repair.
M10-1.0 is commonly used for threads for diesel engine glow plugs, so there are parts out there to fix this size thread.
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Re: 912S Reduced Oil Pressure.
by bill martin » 13 years ago
Mike,
Never seen a Time-Sert before. I think you are right, it looks like a much more robust and permanent fix than a helicoil.
Bill.
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Re: 912S Reduced Oil Pressure.
by James Ott » 13 years ago
Thanks for the suggestions, but I am real nervous about attempting a repair of the threads myself. If I go ahead and try it and am not happy with the result I have then given up any chance of a warrenty claim with Rotax. This is a brand new engine on a brand new Kitfox SS7 and I want things to be right.
You say I will grow old waiting for Rotax replacement parts. How long do you estimate this would take?
Jim
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