Inspect your oil sending unit...and stuff!

[Island Pilot]

Dodged another small bullet yesterday. Went treetop flying for the afternoon and about an hour into it I could faintly smell oil burning. Pressure was perfect, temp perfect and no smoke anywhere. Landed at KORS just because I had one of those gut feelings.

Sure enough, I was dripping oil from the cowl right below the exhaust - looked in the oil filler hatch and could see it had been leaking from the sending unit. It looked attached, maybe loose? Total oil level was fine so I shot back to my hangar, pulled the cowl.

It seems that just the 120 hours of vibration was enough to rattle the 1/8" copper tube so it cracked at the motor/sending unit. I've done cowl off run ups to check for leaks after oil changes etc too so that probably didn't help. In fact we did another cowl off run up while dynamically balancing the new Cato prop. Everything "looked" secure.

Fortunately it was a simple fix yesterday: cut the copper tube, replaced the little round seal but this time I SECURED the bulk of that coiled tube to keep it tied to the nearby engine mount etc.

It could have been a longer down time had it happened on a trip (or worse, if the oil started squirting on the exhaust) - it felt nice to catch it soon, just because I could faintly smell oil burning.

Anyway, it seems like all my bullets come in small, preventable fixes - like the missing cotter pin on a throttle linkage crown nut I discovered on my brand new IO-360 200hp on my RV-7. I bought the plane new but built and put a couple hundred hours on it when one day while changing the oil, I was just looking the bottom of the engine and linkage over while waiting for the last drop to drip and saw the throttle linkage crown nut without a cotter pin!!!!

That could have been a horrible surprise eh? Imagine no throttle control on take off, or landing or flying over unfriendly terrain. Bummer was it was only one little tiny cotter pin.

Pete, I don't know if you guys secure that copper oil line from the sending unit down now (I have the #2 Carbon Cub off the line) but fella's I think it's a good idea because there's a little weight in that loop of line hanging in mid air and it doesn't take much to crack a puny 1/8" copper line.

Simple stuff! Ugghh....it reminded me yet again, it pays to pay attention - all the time.

[Pete D]

The oil press line should be secured to the dip such tube with two zip ties, one around each tube and through each other. The loop of tubing is critical to the setup, allowing the tubeing to flex as the engine shakes over a larger section of the tube, spreading the load out. Should be standard setup on a Carbon Cub, though the early Sport Cubs had a service bulletin on adding the zip ties. Can't recall the number right now but out would be in the service section of the website.

Pete D

[RanRan]

The oil press line should be secured to the dip such tube with two zip ties, one around each tube and through each other. The loop of tubing is critical to the setup, allowing the tubeing to flex as the engine shakes over a larger section of the tube, spreading the load out. Should be standard setup on a Carbon Cub, though the early Sport Cubs had a service bulletin on adding the zip ties. Can't recall the number right now but out would be in the service section of the website.

Pete D

Pete, tightening a 1/8 hydraulic line without disconnecting the other end of the line is going to result in twisting the line...and even then. The rule of thumb is: if it ain't leaking, don't tighten it...but it's so irresistible to think that a quarter turn here and there is improving the situation.

[Island Pilot]

Thanks Pete - I did just that, secured excess line / loop with zip ties (without seeing a service bulletin) and it looks like that should solve it.

The oil press line should be secured to the dip such tube with two zip ties, one around each tube and through each other. The loop of tubing is critical to the setup, allowing the tubeing to flex as the engine shakes over a larger section of the tube, spreading the load out. Should be standard setup on a Carbon Cub, though the early Sport Cubs had a service bulletin on adding the zip ties. Can't recall the number right now but out would be in the service section of the website.

Pete D

[Pete D]

Pete, tightening a 1/8 hydraulic line without disconnecting the other end of the line is going to result in twisting the line...and even then. The rule of thumb is: if it ain't leaking, don't tighten it...but it's so irresistible to think that a quarter turn here and there is improving the situation.

The line is 1/8 copper tubing with nut and ferrule on the end....

Don't think I said anything about tightening the line, just securing it with ties. My main point was the loop needs to be loose in order to shake with engine vibration, but the end needs to be secured so the stress does not concentrate at the end of the line.

Pete D

[RanRan]

The line is 1/8 copper tubing with nut and ferrule on the end....

Don't think I said anything about tightening the line, jusy securing it with ties. My main point was the loop needs to be loose in ordet to shake with engine vibration, but the end needs to be secured so the stress does not concentrate at the end of the line.

Pete D

Is there anything like a heat-resistant plastic line that could be used to better withstand the vibration?

[Dan L]

Is there anything like a heat-resistant plastic line that could be used to better withstand the vibration?

I'm going to use an FEP flame resistant plastic tube made by Parker. It is a non-flammable/UL 94 V-O self-extingushing flexible tube. Holding a section over a flame as a test proved that it just turns black, it won't burn. And I'm going to put a white-stripe flame resistant anti-chafe sleeve over that. Mine is 1/4" OD.

It looks and bends like normal plastic tubing. And it uses regular brass tubing fittings. On my fitting coming out of the engine I soldered a fuel primer nozzle with its small diameter discharge hole acting as a flow reducer just in case the line separated at some point.

I'm also using this same tubing for the manifold pressure line from the engine cylinder to the Plasma III boxes.

[RanRan]

I'm going to use an FEP flame resistant plastic tube made by Parker. It is a non-flammable/UL 94 V-O self-extingushing flexible tube. Holding a section over a flame as a test proved that it just turns black, it won't burn. And I'm going to put a white-stripe flame resistant anti-chafe sleeve over that. Mine is 1/4" OD.

It looks and bends like normal plastic tubing. And it uses regular brass tubing fittings. On my fitting coming out of the engine I soldered a fuel primer nozzle with its small diameter discharge hole acting as a flow reducer just in case the line separated at some point.

That's a much better solution, Dan. Maybe improved by Teflon connectors rather than brass.

But considering the dangers of a leak as the Island Pilot has pointed out, doesn't an electronic sender make more sense in terms of safety and peace of mind? I know these are Cubs, but this is 2011, not 1951. Wires don't leak oil.

Why continue to play this game as if everyone were flying battery-less J3's? Silly game.

Just asking.
Ran

[Dan L]

That's a much better solution, Dan. Maybe improved by Teflon connectors rather than brass.

But considering the dangers of a leak as the Island Pilot has pointed out, doesn't an electronic sender make more sense in terms of safety and peace of mind? I know these are Cubs, but this is 2011, not 1951. Wires don't leak oil.

Why continue to play this game as if everyone were flying battery-less J3's? Silly game.

Just asking.
Ran

My oil pressure/temperature gauge is an EI OPT1 unit. The pressure transducer will mount on the firewall so there is a short pressurized line from the engine to the transducer. Wires then run from the transducer to the instrument in the panel. EI explicitly tells the installer not to mount the transducer on the engine due to problems with vibrations. I'm also Tee-ing a pressure switch into the oil line at the firewall to operate an hour meter.

[turbopilot]

There must be different versions of the oil pressure sensor in the CC. Seems that I have the pressure sensor attached to the right side of the accessory section. Is this something unique to the Dynon option?