Oil Quick Drain Leak Issue

[jlunseth]

I am posting this so others can learn, sort of in the "Never Again" category. 

I have a turbo, and after an oil change and other work in May noticed that I seemed to be leaving some oil on the underbelly.  I read online and was also told by my local MSC, that this is not uncommon in turbos during prolonged WOT climbs to higher altitudes.  The engine tends to blow some oil out the breather tube that vents just behind the cowl flaps.  So I religiously filled to 8 qts. for the longer flights, and cleaned the oil off the belly.

Had a second oil change in July, and this time we noticed a small amount dripping onto the nose tire after a couple of hours of flight, although the dipstick did not indicate any significant oil loss.  I immediately had it checked out by my local A&P and they said it was the quick drain, that they sometimes leak small amounts, and that they had tightened it a little, they said it would not be an issue.  For those not familiar with quick drains (I was not), it is a drain fitted into the drain hole of the crankcase in lieu of the drain plug.  It has a fitting so that a tube can be put on to drain oil into a bucket during an oil change without splashing.  The quick drain can be tightened or loosened by hand.   Easier on the mechanic doing the work.

We then took a long flight (to one of the MAPA PPP's, but that's another story).  After about three hours in the air I noticed a substantial drop in oil pressure and we made an immediate landing (that's another story also).  The bottom of the plane was coated with oil. 

The A&P where we landed initially said there was no oil left, but when they pulled the quick drain, something over 3 qts. drained out.  The quick drain has a hole in the side through which the oil enters the drain, then drains down through the drain.  I would say the hole is about .33 inches in dia.  A small piece of plastic swimming around in the oil had gone through the hole and prevented the quick drain from completely sealing.  The plastic was roughly a third of an inch long and maybe a sixteenth of an inch wide.  It looked like a piece from the ring on a plastic bottle of oil, the ring just below the cap where the cap separates from bottle when you unscrew it.  It was thick enough to hold the quick drain just slightly open when the mechanics thought it was tight.

In addition, the reason no oil drained out when the mechanic at our point of landing initially opened the drain, was that there was also a small piece of rubber, fairly thin, about a half inch wide and maybe an inch long, that appeared to have plugged the drain.  Who knows, maybe that second piece is what prevented us from losing all the oil.

Now that the quick drain leak has been corrected, the initial "oil blowing out the breather tube" issue that we were seeing also seems to have gone away.  Apparently what was happening was that WOT climbs to altitude were indeed pressurizing the engine, and maybe some oil was going out the breather tube, but the biggest loss was oil going out through the quick drain.

I haven't personally performed any oil changes, even on my car, for quite a few years, apparently before the advent of the "quick drain," so I didn't even know what a quick drain was and had no idea my engine was equipped with one, let alone that they can leak in this way.  The bigger piece of rubber found in the crankcase was, according to the mechanic and after looking at the logs, something that probably entered the engine 7 or 8 years ago, before I owned the aircraft, so that rubber had been swimming around for some time apparently unable to leave the crankcase at oil change time because of the small size of the quick drain hole.

My plane has been annualed several times since then, and this past spring was annualed by a very good MSC.  So apparently A&P's are not in the habit of removing the drain itself, not even at annual time.

I have thought about just removing the quick drain and installing a regular drain plug, but quick drains are useful devices.  I think from now on though, I am going to have my mechanic pull the quick drain at every annual to make sure that anything that gets into the engine oil has an opportunity to leave at least once a year.

Last winter I had an EDM 930 installed in the aircraft, on the pilot side of the panel, so that the engine gauges would all be in one place in front of the pilot for inclusion in my scan.  Good thing, I caught the pressure drop early and before any "low pressure alert" went off.  Had we continued flying very long it could have been a different situation.

[carusoam]

JL,

Very interesting piece on quick drains.  There are new versions of the quick drain vs. the old style.  The new ones are machined and appear to be precision made.  It appears that 1/4 turn with a locking device operates the valve.  The old ones are stamped and held in place with a spring.

My  O -360 quick drain always had a drop of oil hanging from it.  I was studying quick drains to see what I would replace it with.  Never got there though....

http://www.aircraftspruce.com/catalog/eppages/safOilDrainValves.php

It looks like a good idea to have help selecting the proper one....

-a-

[jlunseth]

I looked at your link to Aircraft Spruce.  Mine looks very much like the blue anodized units in their catalog.  I had that thing checked out by three mechanics including one just before the flight with the problem, and they all said the same thing, "Don't worry, quick drains leak a small amount."  Famous last words.

[Immelman]

Very interesting. Can you tell me one piece of information: Did the engine get run after new oil was added (i.e. at the oil change preceeding this event), and then was the quick drain examined for leaks? In other words, did it pass a leak check and then open up later on, or was there no leak check?

[fantom]

Most quick drains DO leak a very small amount, and completely removing a quick drain isn't part of an annual, so you can't fault the A&P.

Good story, that 930 and a bit of luck came in very handy, and the more you know about what's under your cowling the better off you'll be. Glad it worked out for you.

[jlunseth]

To answer Immelman's question about what was done to verify no further leakage, the A&P, with me present, cut the first filter and verified no metal, then we refilled the oil with a new filter, ran the plane up, cut that filter, no metal, than refilled the oil a third time and verified no leak from the quick drain.  The plane then sat for a few hours while we got ready to depart, I preflighted and checked for the drips on the nose gear, no leak.  The remainder of our flight was two short legs with landings and the nose gear was again checked for leaks each time, none present.  I then spent the rest of the weekend at the Mooney PPP, flying the plane for around two hours each day, again checking for leaks during the pre-flight and none present.  We have now flown about 16 hours since the oil was refilled/changed and it is safe to say that I preflight every time and look for any evidence of leakage of any kind.  My copilot also now knows what the oil pressure should be, so she watches it quite a bit even when I am not.  The oil loss I was experiencing in WOT climbs to the teens prior to this occurence appears to have stopped also, although I have not had occasion to climb to the teens yet, just up around 9000 a few times, so I will be watching that to see if I am still losing oil through the breather, which I understand is fairly normal.

To answer fantom's question, I am not seeking to fault anyone.  I mentioned the A&P so I would not get the inevitable question, "Why did you take off with an oil leak?"  We had the quick drain checked two times by A&P's, including just before the flight, and the mechanics all said the same thing, that quick drains leak and it is not an issue.  So we concluded that everything was normal. 

The engine was thoroughly checked out and it was not hurt.  Although we saw low oil pressure, we never saw high temps and the engine was throttled back for our rapid descent to landing to both slow us down and to save the engine. I just wanted to let people know so that if you have a quick drain, its removal does become part of the annual.  It will be part of my annual from now on, I guarantee it.  Fairly obvious this one had not been removed in several years, and also fairly obvious the failure to remove allows material to collect in the crankcase that can then keep the quick drain from fully sealing.

Did I mention we had to descend rapidly in IMC from 19k?  To an unknown airport not in my database?  On vectors?  In Canada with no passports and no eAPIS filed?  Had to negotiate with US CBP and Homeland Security to get back into the country?  Land at a Class Charlie with the jets to get back in?  As a pilot, you can get stressed out about these kinds of things, or you can see them as adventures and learning experiences, or you can get stressed out and also see them as adventures and learning experiences.  What I really liked about the whole thing was the guy driving the fire truck in Ont., who called me "Captain."  I am grateful I was trained right, and maybe for a moment in time I deserved the title.  Its fine with me if life returns to normal now.   

[scottfromiowa]

Glad you got down safe, didn't damage plane and got to the bottom of the problem.  Perhaps this should be brought to the attention of the oil/bottlers to prevent/minimize a chance for re-currence?  I added a quart of X/C this weekend before return flight from Arkansas.  I have the extension that comes in the case and had a hell of a time removing the cap band to install the extension...Probably on there extremely well to reduce/minimize potential for such an event?  I am VERY careful when I open a quart to include pop/milk etc...to make sure nothing falls back in the container.  Your clog at the quick relief was a reverse choking hazard...almost choking the oil/lubrication from your engine.  I commented that I thought the alarms in the newer engine monitors were "nice", but not NECESSARY...(vs old GEM separate post)  Here is a perfect example of how the cost of a improved monitor saved an engine, an airframe...and perhaps injury(s).  I am swaying toward the update with a latest greatest regarding engine monitors.  GREAT POST!

[jlunseth]

The alert level was set to 10 psi, so we did not see an alert on the 930 until we had already discovered the problem, throttled back, and nosed down. I suppose it is that low so as to avoid alerts while taxiing with a warm engine.  I have to say, I would probably not have seen this with my old strip gauges that were scattered all over the panel, poorly lit, and inaccurate anyway. With the 930, you find yourself constantly checking the panel to watch the EGT's and CHT's, so you take in all the other engine functions as well.   

I use XC also.  This was black plastic, so Aeroshell or something like it.  I guess that is another issue, I will endeavor to make sure the ring is gone before I pour oil into the crankcase in the future.  But I believe there is a screen to prevent particulates from trying to circulate through the engine to the bearing, etc.  Instead, they swim around in the crankcase until there is a big enough drain hole to allow them to depart.

If anyone wants to look, go to flightaware, put in N381SP, and look for the "result unknown" flight from KFCM to KIAG (never reached KIAG) on 9/9/10.  Highlight it, then click on "track log & graph," and scroll to the graph and data at the bottom.  You will see what a rock looks like when it drops from 19k, or a Mooney with speedbrakes, same thing.  We had about 20 miles to lose 18K with a 50 kt. tailwind.  We usually need more like 75 miles to do that elegantly.  I did hurt my copilot's ears a little. 

PS if you do look up the flight, no we were not diving at 220 knots, which would be over the NE speed.  We had about a 50-60 knot tailwind which was nice until we needed to get down.  Our TAS in the dive was short of the top of the green arc.  Did I mention I am also grateful for an airframe that does not have parts departing at those speeds?

 

[mooneydriver]

When I changed the oil on my 76 F model the first time after purchase , I noticed a rubber plug pushed into the Quick Drain. I had not seen this before on other planes I have owned or serviced. After thinking about it I liked the idea and replaced the plug after changing the oil. The plug will keep something similar to what happened to you from occurring.

 

Rick

[jlunseth]

Maybe, but I kinda doubt it.  The oil was being pushed out under pressure, and there was alot of it.  Would have blown out a push in plug.