New Mooney owner seeing oil leak?

[ZamF16]

I am the proud new owner of an '89 Bravo.  I love the stability, power, and performance...much more than I expected.  One concern I have is oil that appears on the nose gear door after every flight.  I keep wiping down the gear door and nose gear, but I see oil streaked across the door and on the underbelly that is making me nervous.  Also, seeing oil that drips onto the nose wheel between flights.  The A&P that did my pre-buy does not seem too concerned, but I wanted to see if this was normal/expected from those of you that are experienced Mooney owners.

Thoughts?

Dave

[Skywarrior]

Mine does the same thing. A&P said not to worry.

[jlunseth]

I was going to say don't worry until I saw the line about oil dripping on the nose gear.  Streaks are not uncommon, and ordinarily are caused when you check the oil or add some, and drip a drop or two into the engine compartment.  That finds its way to the exterior, and a very small drop can become a long streak on the exterior.  Dripping on the nose gear, however, requires immediate attention particularly to the oil quick drain.

My Mooney was using too much oil I thought, about a quart every 7 or 8 hours, particularly when I made full power climbs to altitude.  A & P's said that is typical.  One day after an oil change I took a brother of mine up on a flight, and we saw a few drips on the nose wheel.  Being a mechanic (not aircraft), he is the person who picked it up.  Since the plane was not losing more than the amount of oil I was told was normal, I flew it home and had an A&P check it.  I was told it was normal for quick drains to drip a little. 

A couple weeks later I and my co-pilot were going to overfly Lake Michigan going eastward to a MAPA PPP at Niagara Falls.  During the pre-flight, I saw the drip again, so I had the local mechanic (different from the first one), remove the cowling and check it.  Same story, it is normal for quick drains to drip a little.

So we departed.  The trip over Lake Michigan was fortunately uneventful, but shortly after the lake we were overflying Canada, it had gotten dark, and we were flying into the backside of a front so we would be over IMC at FL190.  Scanning the instruments, I saw that the oil pressure was 14 psi.  It should be at least high 30's in my aircraft.  I knew immediately that the oil leak we had seen was not normal, and that we had an emergency.  So we declared with Toronto ATC and got vectors to the nearest airport, which was London ON.  I did not know if the engine would keep running for another minute, and I did surmise that we had blown a good deal of oil out into the engine compartment, where it was probably misting and covering things it shouldn't, like the turbo collector, which typically runs several hundred degrees F, if not over a thousand.  I throttled back to preserve the engine in case we needed to maneuver to a runway, and we had to make an emergency rapid descent because London was only about 20 miles away, we were at 19, and the winds aloft were around 65-70 kts. from the west.  When I tipped the nose over the oil pressure dropped to 6 psi, I had expected that because what oil remains will run away from the intake, but it was disconcerting anyway. About 7,000 feet of the descent was through thick IMC completely on instruments and in the dark.  The way we found the airport when we broke out was the lights on the crash truck.  Made a perfect landing, and the driver of the crash truck said, "Nice job, Captain."  He knew I was not a captain of anything, but it was a compliment and that particular night I maybe deserved it. 

The story got more interesting after that, because we had no passports and no means of filing an eAPIS manifest to re-enter the US.  But that has nothing to do with the mechanical event.

The next day, the local A&P reported that my engine was dry of oil.  I probably turned gray.  I said that couldn't be possible because I had checked the dipstick after our landing and there was oil on the very tip.  Not much, but should be about three quarts.  He took the oil quick drain out, and found the problem(s).

First, a small sliver of plastic that looked like one of the plastic fingers from an oil bottle cap, had entered the side hole of the quick drain (the inlet), but was too long to pass through.  It allowed the quick drain to almost close, but kept it open enough that when the engine ran and the crankcase was pressurized, oil blew out the quick drain.  (The bottom of the aircraft had been covered when we landed, it was dripping off the tail.)  Then he also found a larger piece of rubber that he said was a part of a gasket that seals the hole the valve rod goes through, and if a new cylinder is put on and not installed exactly correctly some of the gasket can get shaved off.  The only cylinder replacement that had occurred, was several years earlier before I owned the aircraft, so that piece had been in the crankcase for awhile.  The gasket piece had been large enough to cover the hole in the quick drain, and probably prevented all the oil from departing, so there was about two and a half quarts left.   Turned out the engine was fine and we were free to try to get back into the US. 

I am telling you all this in detail so you understand that drip on the nose gear is not to be played with, and you should not go with any A&P's statement that it is normal.  If the breather hose on your model discharges over the nose gear, maybe.  But I don't think that is true on any Mooney model, it would wreck the nose tire.

What needs to happen is that you need to have the oil changed.  When you do, tell the A&P that you want to have them remove the quick drain and allow the oil to drain out through the full sized crankcase hole.  Then have them install a new seal kit in the quick drain.  At a minimum have them disassemble the quick drain and clean out any debris, even if no new seal kit.  I now have my A&P remove the quick drain and drain the oil at every annual to make sure that anything swimming around in the oil can depart the crankcase.  I would suggest that to any other aircraft owner.

Your plane and your life.  Streaks are not necessarily a worry.  Drips on the nose gear are a worry.

[carqwik]

Any time something is out of the ordinary, that is enoughreason to investigate and starting looking for the causes.

Last week, my Bravo was having problems holding RPM....setting it for cruise at 2400 RPM, a minute or so later I'd see the tach read 2300.  Reset to 2400...a minute goes by...it's now showing 2500.  This is totally out of the ordinary as the rpm varies at most about +/-10 RPM once set.  Considered landing immediately but RPM would just settle at some number and hold there...worse case was that it would default to max RPM and there were plenty of airports around.

Thought it might be the friction lock on the prop lever but that checked out fine.  Removed the cowl and my mech immediately saw the problem...a bolt had worked loose on the linkage from the governor to the prop cable.  This looseness explained why it RPM would not stay at a set value...  Took two minutes to tighten bolt and install new safety. 

Leaking oil dripping from the cowl (other than from the crankcase breather) needs investigation.  My two cents...

[ZamF16]

Thanks all for the advice.  I don't have enough SA with this airplane to know what is out of the ordinary, but it sounds like I should at a minimum pull the cowling and see if I can find the source of the leak, and perhaps have the quick drain pulled out and looked at for foreign objects in the crankcase. 

[Earl]

I own a 252 and when I have more than 6.5 quarts it spits it out the breather tube but I still get 10-12 hours per quart and has in the 300 hours I have on the plane.  But that oil is never on the front gear but does get on the back part of the gear door where the breather tube discharges.  Oil on the front gear would make me very nervous and I would have it checked by an A&P as soon as possible

[johnggreen]

jlunseth,

I wan to compliment you on one of the most valuable posts I have read on a maintenance/safey issue in a long, long time.  It will impact how I have maintain my Bravo.  This is what a blog like this should be about.  Knowledgeable people reporting on real life EXPERIENCE.

Thank you again,

Jgreen

[FoxMike]

Sometimes during a oil filter change oil leaks onto the low point of the firewall.  When you are flying the oil gets sucked onto the gear doors.  Of course, it could be something else so  a little investigation is worthwhile.

[bnicolette]

Is it absolutely oil?  I sometimes get hydraulic  fluid on the left nose gear door from the master cylinder?

[jetdriven]

Our J did that when we first bought it. Oil on the nose gear door. The rubber connnectors to the pushrod tubes were leaking. I dont know if that applies to a Bravo. But worth a look?

[jlunseth]

Quote: johnggreen

jlunseth,

I wan to compliment you on one of the most valuable posts I have read on a maintenance/safey issue in a long, long time.  It will impact how I have maintain my Bravo.  This is what a blog like this should be about.  Knowledgeable people reporting on real life EXPERIENCE.

Thank you again,

Jgreen

[Chessieretriever]

We have a Bravo with the Rocket 351 conversion. Although our engine is a liquid cooled TCM unit I imagine that the problem we experienced could be similar in a Lycoming power plant. So for the benefit of other members I will share our experience and the outcome as well.

We had the same syptoms (for months and 100+ hours of flying) you describe and attributed the drops of oil on the ground after pattern type flying (to perfect LOP etc.) to engine oil coming from the breather when using aggresive climbs (above 1000fpm) as there was a bundle of oil hoses tied together on the pilots side of the front gear door (including the the vent from the engine) . Then we experienced a reduction in oil pressue in flight like you described, landed and found that we had lost 6 of the 12 quarts of oil that we started with. The culprit in our case was a diaphragm on the waste gate. It turns out that many aviation engines (ours included) use engine oil pressure to help regulate the manifld pressue (in addition to a spring). Oil under pressue from the engine is routed to a chamber on the waste gate which is separated from the outside by a diaphragm. There is a return oil line which is connected to a valve wich is regulating how much of this oil is drained back o the sump and in so doing effectively regulates the oil pressure in that little chamber. The more oil pressue is in that chamber results in the waste gate being more closed (higher manifold pressure); the opposite being the case for the open position. There is a smaller line on the waste gate that is vented to atmosphere and tied to the rest of the rubber lines coming out of the engine compartment. The idea is that if or when there is a leak in the diaphragm then the oil that leaked out goes into this little oil line and then to atmosphere with the indication that you have an oil leak (otherwise it would leak past the actuator on to the hot exhaust manifold and pose a fire hazard). Well in our case the diaphragm ruptured and all of the oil from the engine being pumped to the waste gate ended up on this little line and out the bottom of the airplane. It happened onthe descent to a landing so we did not realize that the low manifold pressure was not only the lower throttle setting but the waste gate being fully open. We changed the waste gate and solved the problem. I am attaching a picture of the waste gate with the two larger oil supply/control lines and the smaller oil "vent" line. By the way the same waste gate is used by many Lycoming engines (I learned when looking for a replacement). I hope this helps others which may encounter these type of problems in the future.

Cheers, OFM

N9154W, N92AV

P.S. Could not post a picture due to my own computer limitations. If you need one please PM me so that I can send it via e-mail. Sorry

[carusoam]

OFM,

Thanks for sharing. Very interesting lesson on waste gate control.

If you want, email the pictures to me, I should be able to upload here.

My email addres is in my profile.

Best regards,

-a-

[Tony Armour]

A couple times I have had a leak from one of the oil nozzles that goes into the head on the top (the Bravo mod) Mine has been cylinder #3 and it would end up as burnt oil on the exhaust and on the right main gear door. Even though the leak is on top, you really can't see it on the top. Easy fix too.

[ZamF16]

All, thanks for all the advice.  The oil leak got progressively worse until I was dumping almost a half quart an hour across the bottom of the aircraft...really getting messy.  Pulled the cowling and found the accessory area behind the engine soaked with oil.  Couldn't find obvious leak, though.  Had inspector take a look...found that a magneto and the distribution cap were both loose and getting worse each hour of flight allowing the leak to get progressively worse.  Now I am back to using a quart every 5-6 hours and feeling much better.  No more oil under the aircraft at all.  I learned in this process that I have an air-oil separator installed, so the oil under the aircraft should be very minimal.  Again, thanks for all the advice.

[johnggreen]

Zam,

Thank you for the update.

It's a good idea to consider ANY change of behavior/operation of an airplane as a possible harbinger of trouble.  It usually is.

Jgreen