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Mystery oil leak in Jab 2.2


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Wilco, OT. This hose is only a few months old, but maybe it was a dodgy one. Perhaps this time I'll get Pirtek to make up a set of threaded fittings. It's due for an oil change next month anyway.

 

My other problem is less serious, but just as perplexing. I went to lots of trouble to install a low oil pressure switch to give instant warning of a leak, such as a ruptured hose. The damned thing is back to front to what I expected: when oil pressure reaches the set reading it closes a circuit, so the plurry red LED only comes on when everything is hunky dory! Repco aerospace didn't tell me that part.

 

it cost me over $60 and several trips to get the correct adapters, so I'd like to keep it.

 

Can it be wired so that the light goes off when oil pressure is okey?

 

I only use USA hose or the Rotax ones (In my case a rotax engine)  USA quality for the other hoses.  Cheers.

 

 

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Hi Old K, 

 

If you put a change-over relay in the line it will get the light to work the way you want it. It will require a couple of wires but I'll do my best to 'farmer-splain' it. I'm not an auto-elec so be warned...

 

Refer to below diagram

 

For Positive feed

 

30-  +pos taken after master switch

 

85-86 cut the +pos or -neg to oil switch and insert relay in this line. I'm pretty sure power only flows one way through this circuit so 85 should be closest to battery +pos

 

87- not used (cover with something non-conductive as this will be +pos during normal operation, or use a green LED to indicate pressure OK)

 

87a- connect to the +pos in on the red LED.

 

You could use 30 and 87a to 'earth' the Red LED if that better suits the current wiring. That way 87 would not pose an issue with sparking as it will hold no current under normal operation.

 

As for the oil leak, I've seen oil/coolant appear to be sucked toward the fan on large engines due to back pressure behind filters etc. With that theory the leak could originate above and slightly behind where you think it is coming from. I'm not familiar with the Jab engine so I'll leave it at that. 

 

I've had oil filter o-rings blow as described earlier. Never had one re-seat itself. 

 

Hope this helps.

 

Cheers

 

Prop

 

68070-Dim.png

 

 

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Prop Farmer your farm-splaining did it for me. Thanks, I'll try that.

 

Re the oil leak, the Jab engine is simple and most of it easy to inspect. Given the great steaks of oil I found running back with the prop wash, I can see only two likely sources:

 

The O ring behind the oil filter, or as OT suggested, a failed oil cooler hose. All the testing I've done since was on the ground, within a max. of 1900rpm and only 250kPa on the clock. At cruise it reads 350 at 2800rpm, so maybe hotter oil at higher pressure will reopen the leak.

 

Why it suddenly allowed 200ml to leak out, then re-sealed itself is the mystery. 

 

 

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Why it suddenly allowed 200ml to leak out, then re-sealed itself is the mystery.

 

 

And that type of weird behaviour is exactly why I think the hose is quite likely to be the culprit. Rubber hoses can leak, and then reseal themselves, as the rubber moves around.

 

 

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The if the globe is a dud it's all OK, OK.? The current logic is sound.  but the light should be green.  Landing gear lights are the same and it's the convention. You have bulb test facility Press to test or two bulbs. per indicator.  Nev

 

 

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Prop Farmer your farm-splaining did it for me. Thanks, I'll try 

 

You could also put a resistor from the poitive bus to power the lamp with the switch wired across the lamp so when the pressure switch closes the lamp is shorted directing current through the resistor.......if it's an Led then only few mills would be needed, adjust the resistor value to suit.

 

 

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One theory.....

 

The oil pressure control valve (ball and spring?) May have had the ball stuck for a few seconds overpressurising the system for a second or two.

 

 

 

Not a theory, happens quite often to engines sitting for periods of time.

 

Sometimes the telltale is an expanded oil filter, they get a little fatter in the middle from the pressure.

 

Other times is when the oil filter splits and you spend a half hour cleaning the floor ...

 

 

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The if the globe is a dud it's all OK, OK.? The current logic is sound.  but the light should be green.  Landing gear lights are the same and it's the convention. You have bulb test facility Press to test or two bulbs. per indicator.  Nev

 

No Nev, the plurry light is fine-just ON when it should be OFF.  Repco Aerospace didn't tell me it was the ON type- I didn't know they existed. 

 

I might toss it ($64 and lots of hassle wasted) and get an OFF type. I plan to get Pirtek to replace my hoses with threaded couplers, and they can tap the new switch into the oil cooler collar. Simplicity matters.

 

 

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One theory.....

 

The oil pressure control valve (ball and spring?) May have had the ball stuck for a few seconds overpressurising the system for a second or two... Perhaps some oil residue of some sort sitting around the ball.

 

I presume that’s what’s housed in the circular item under the prop.

 

It hasn’t been cleaned in over a decade/250+ hrs of service, so I might do that.

 

My prop, spinner, etc. all have to come off first. That gives access to the two forward-facing holes near the oil filter: do they are tap into the oil system, so I can mount a low pressure switch there?

 

 

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 Sorry to persist, but a warning with the light coming ON is not a reliable indicator. unless it's duplicated . On the thinking it would be unlikely that two indicating systems would fail at the one time..

 

       A light showing all is OK (functioning) gives a continuous assurance. ALL things have to be right for it to be on, and I gave an an example. Landing  gear  where the indicators shown a position Ie DOWN and LOCKED for each leg and in addition is an agreement light as the selector lever position is part of the equation.'

 

      Anyhow it's a question of which "LOGIC" appeals to you at the end of the day  If you rely on an array of red warning lights you usually have a press to test switch that brings them all on..

 

  An oil pressure gauge, once you get used to how it reacts to hot days, power changes and low levels of oil, can be  more informative than any warning light.  IF indicator systems are not reliable they are an extra hazard . Nev

 

 

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 ... A light showing all is OK (functioning) gives a continuous assurance. ALL things have to be right for it to be on..

 

True, but which is more likely to get my attention: the sudden appearance of a bright red light, or the sudden absence of a green one?

 

  ...If you rely on an array of red warning lights you usually have a press to test switch that brings them all on...

 

The light will be tested every time the engine is started- just like a car.

 

...An oil pressure gauge, once you get used to how it reacts to hot days, power changes and low levels of oil, can be  more informative than any warning light...

 

Of course. That's why I'll have both.

 

 

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