Mystery oil leak in Jab 2.2

[Old Koreelah]

Hello all. Perhaps someone can figure this out for me.

 

Yesterday as I was warming up my engine prior to departing for Austfly at Narromine, I noticed a big oil smear being blown over my floor windows by the prop blast.

 

After shutting down and removing the cowls, it was obvious that lots of oil had suddenly leaked out in the vicinity of the oil filter. It had been blown all over the lower half of the engine, over-filled my belly cowl and was pouring onto the tarmac.

 

It took about 200ml to bring the dipstick reading back to where it was before startup.

 

After a thorough cleanup, I restarted the engine for a few seconds, then stopped to inspect for oil leaks. None. Running the engine for progressively longer periods still resulted in not a drop of oil appearing.

 

Mystifying.

 

The only change I had made to the engine was to cut a 90degree T junction into the oil cooler hose, so I could fit a large workshop oil pressure guage. The engine ran happily with this for nearly half an hour of taxiing around (that instrument agreed with my panel gauge, so I'm happy about that).

 

After that test I replaced the big gauge with a small low oil pressure switch, rated at 180kPa. I wired it to earth out a bright LED on my panel, to give me instant warning of a pressure drop, such as due to a ruptured hose.

 

I cannot find any evidence of oil leaking around any of the new connections.

 

Aside from the mystery oil leak, the new sender seems to be back to front: the plurry warning light only comes on when the engine is running!

 

Any thought gratefully received.

 

 

[facthunter]

How much flying is your kite getting these days? You might have a bit of bore corrosion and blow by.  Nev

 

 

[Old Koreelah]

Not a lot, Nev. Probably average two hours per month.

 

The oil leak was sudden and seemed to come from behind the oil filter, not the engine breather.

 

 

[biggles]

Was the oil filter loose or filter adaptor O ring not sealing ? Did you tighten the filter? . Had you changed oil etc. ? ..... Bob 

 

 

[turboplanner]

Did the ends of the T Junction have a ridge around them?

 

If so, you may not have tightened one of the hoses enough and it has been squirting oil, then the hose slid along untilthe clamp was up against the raised section and blocked the oil leak.

 

 

[Old Koreelah]

Was the oil filter loose or filter adaptor O ring not sealing ? Did you tighten the filter? . Had you changed oil etc. ? ..... Bob 

 

Can't say for sure, Bob. It's hand-tight only. The oil appeared to have come from under that O ring, but nothing since I cleaned it up.

 

Did the ends of the T Junction have a ridge around them?

 

If so, you may not have tightened one of the hoses enough and it has been squirting oil, then the hose slid along untilthe clamp was up against the raised section and blocked the oil leak.

 

 Interesting possibility, Turbs. The T has barbs, which are quite effective (I had reason to remove it before I added the hose clamp and it was a much harder than inserting it).

 

it occurs to me that there might have been a momentary blockage of the oil system that forced a big leak around the oil filter O ring. While installing the T junction a tiny bit of fibreglass fire-proof material got into the line. I believe I got it all out, but even if I didn't, I can't imagine it caused this event.

 

I have to take some kitty litter and cement powder to the airport tomorrow- oil spills are not good for the tarmac.

 

I'll get her out again and do some more investigating.

 

 

[biggles]

I’ve seen a similar thing happen where the operator got distracted, and wire from the oil pressure sender got caught under the edge of the adaptor, causing the O ring to not seal . Easy fixed but Oh what a mess ! ..... Bob 

 

 

[facthunter]

 Filter cross threaded or O ring  partly dislodged from it's recess.?   I  "accidently"delayed sending this as have had some computer glitches. Nev

 

 

[Old Koreelah]

Whatever it was, I can't seem to get it to happen again. Old mate David from Terramungamine just called and suggested I go test flying over tiger country at low level- as if Murphy needs tempting!

 

Thanks for your thoughts, people. I have another close look at it tomorrow.

 

 

[Downunder]

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.

 

The seal on the oil filter may have been the first point of failure and popped out briefly. 

 

Cold oil (higher pressure) and sitting for a while may have contributed to this. Perhaps some oil residue of some sort sitting around the ball.

 

Do you turn over, mags off, to get oil pressure first or a straight kick in the guts?

 

 

[facthunter]

Some of those filters have pretty sloppy threads. Nev

 

 

[kgwilson]

In theory cold oil = higher pressure. The pressure increases with temperature on my gauge.

 

 

[facthunter]

 I've seen engines where that happens and it's the reverse of what one would  (normally) expect. It's usually where there's a long run to the suck side of a pump..  Nev

 

 

[Downunder]

Theory two.....

 

Does the oil filter have a bypass valve?

 

Maybe this stuck closed......

 

 

[Old Koreelah]

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.

 

The seal on the oil filter may have been the first point of failure and popped out briefly. 

 

Cold oil (higher pressure) and sitting for a while may have contributed to this. Perhaps some oil residue of some sort sitting around the ball.

 

Do you turn over, mags off, to get oil pressure first or a straight kick in the guts?

 

Interesting. I'm religious about turning the engine at least ten blades to feel for uneven compassion and to get oil circulating.  I sure did perform the ritual that morning.

 

Oil is still very clear, only done about ten hours/5 months, but is due to be changed soon.

 

 

[Old Koreelah]

Theory two.....

 

Does the oil filter have a bypass valve?

 

Maybe this stuck closed......

 

In May I changed the oil and filter. It currently has a proper Z-386, while previously it had "equivalents".

 

I can't seem to get a clear answer about whether the Ryco Z 386 has a bypass valve built in, or if the engine requires one.

 

 

[facthunter]

That's a very common filter. They should only bypass when the element is clogged or when revving cold. Neither of these things are likely to happen in this case. also the bypass is achieved by the entire filtering element moving opposed by a largish, but relatively weak, spring. I would consider it fail safe as the bypass is only to preserve AN oil flow  when you've left the filter change too long or the oil has thickened.. Unfiltered oil then goes through the engine . it's not a very large filter like many these days. I'm now using them on my wife's lawn mower. because only the best is good enough for her.  Nev

 

 

[Downunder]

Interesting. I'm religious about turning the engine at least ten blades to feel for uneven compassion and to get oil circulating.  I sure did perform the ritual that morning.

 

Oil is still very clear, only done about ten hours/5 months, but is due to be changed soon.

 

Turning the engine over by hand probably won't "pop" the ball as you need to reach the pressure it is set at for it to lift. 

 

 

[Old Koreelah]

Just noticed I've accidentally included some politics into my post #15:

 

"uneven compassion" 

 

Stupid predictive spelling again. Tried to say uneven compression.

 

Just got back from the airport where I cleaned the engine thoroughly and ran it for half an hour, trying to illicit some sort of oil leak. Not a sausage, as Spike would say. 

 

Lots of fun opening our hinged hangar doors into gusting 15kt wind. I suspect that more pilots are injured by hangar doors than aircraft prangs. 

 

Downuder's post #10 looks to be the most plausible explanation.

 

 

[facthunter]

 Except that the rubber seal can't pop out if it's in the right place and even moderately tightened. The only way I've had that failure is when the "old" seal sticks to the block and you end up with two seals.

 

  I also can't see how a ball seating can Jamb closed. A plunger one can. . Nev

 

 

[onetrack]

Old K, the Ryco Z 386 has a rubber on steel bypass valve fitted internally. You certainly have a very curious leak problem. However, intermittent and serious leaks need to be chased down and found, for fear of it happening again when in flight.

 

The greatest problem I have found with oil leaks, is trying to find the precise source, because of the way the oil from the leak spreads, and follows grooves and depressions, making it appear to come from some other location, than the actual leak site.

 

I'm inclined to think your rubber oil cooler hose is the suspect. I have reservations about any rubber hose that carries engine oil under pressure, they are the first component to fail, and I've seen more than one engine destroyed because a rubber hose carrying engine oil under pressure, failed.

 

 

[facthunter]

Also a great way to get a fire. Power steering and transmission oil coolers are notorious for it. . Also oil filter cases have split. and as I mentioned earlier some of the thread fits are too loose. A lot of things may seem like luck but the more careful you are the luckier you seem to get . Nev

 

 

[onetrack]

Also a great way to get a fire. Power steering and transmission oil coolers are notorious for it.

 

In my experience, turbocharger oil lines are the greatest source of engine fires. Seen some very large and very expensive machines burnt to a crisp, due to turbocharger oil lines spraying oil onto hot exhaust manifolds.

 

Yes, I've seen oil filter casings split - but generally, once they split, they continue to leak.

 

My advice to Old K is to replace the filter, and the rubber hose.

 

Hoses are made up of inner and outer layers of material, and if a split develops in an inner layer, the oil will often travel down between the layers, until it finds a weak exit point.

 

Inner layers of hose can also fold back on themselves and cause a blockage. I've had that with a brake vacuum hose on a vehicle (the hose between the manifold and the brake booster).

 

The inner layer of the hose peeled off and bunched up, blocking the vacuum off to the booster. I ran out of brake power assistance at a most inopportune moment, and it came as a bit of a shock.

 

 

[cosmicray]

A mystery oil leak with a Jab 3300 turned out to be leaking distributor spindles. Although the spindles are at the rear of the engine the oil ended up all over and coming out of the cowl.

 

 

[Old Koreelah]

 

...My advice to Old K is to replace the filter, and the rubber hose...

 

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?