M20K Rocket Breather Tube-Picture Wanted

[snowds]

Hello all,

For years, my Rocket has suffered from an intermittent excessive oil blowout through the breather tube.  By intermittent, I mean that most flights the oil will coat the bottom of the plane, but only lose a half quart (regardless of length of flight-30 mins or 3 hours); every once in a while, though, it will blow out 2-3 quarts in a 30-min flight, and the bottom of the plane will be dripping oil from the breather tube all the way to the aft tie down.  We have done all of the diagnositics recommended by Continental, including top-overhaul, shaft seal replacement,  dip stick replacement and crank-case pressurization check with an airspeed indicator).  I am coming around to the belief that the problem is an improperly placed breather tube termination.  Does anyone have a Rocket on which they could take a picture of the breather tube termination (assuming you do not also have an oil blow problem).  Also, any educated discussion on breather tube placement would be great; all I can find is that it should not be in a postive or negative pressure area, though guidance on where the positive and negative pressure areas are seems to be more of a guessing game than science.

 

Thanks for any help!!

[David Mazer]

My breather tube is in essentially the same location.  I have almost zero oil use between changes (less than 0.5 qt over 30 hrs) since my OH.  There is a trace of oil on the breather tube but clearly it is insignificant since I never have to put in any oil between changes.  Sorry but I think the problem is somewhere else.

[Marauder]

On my IO-360 the breather has a small hole a few inches above the end of the tube. It was explained to me that it was there to prevent a siphoning effect from air passing the end of the tube. Do your tubes have this as well?

[jlunseth]

Why is the source necessarily the breather tube?  I had the same symptoms from the oil quick drain, debris in the oil would catch in the drain and prevent it from sealing.  Running the engine would pressurize the crankcase and blow oil out.  It would most commonly happen during long, full power climbs to the flight levels.   Not so much if I was not climbing as high.  The debris enters the quick drain, but if just the "right" shape, will not run through the sealing mechanism.  Oil all over the belly.  It would also be episodic, in that it would depend whether the debris was in just the right spot when the drain was opened and then closed during maintenance.  The cure is to take the quick drain out once in awhile, say at annual every year, and allow the oil to drain through the original drain hole.  Cleaning the crankcase if you ever have that opportunity, is even better of course.

[aviatoreb]

Your breather looks like mine as well.  I am sorry to hear of your troubles.  I also have a very tight engine like David, and I add oil only maybe every 30 hours or so.  Actually often I never add oil since then that is around when I do an oil change.

[Alan Fox]

On my IO-360 the breather has a small hole a few inches above the end of the tube. It was explained to me that it was there to prevent a siphoning effect from air passing the end of the tube. Do your tubes have this as well?

If you have bladders , it is part of the installation... As far as the breather on the Rocket , I think Rocket is still in buisness and could advise you....

[snowds]

My breather tube is in essentially the same location.  I have almost zero oil use between changes (less than 0.5 qt over 30 hrs) since my OH.  There is a trace of oil on the breather tube but clearly it is insignificant since I never have to put in any oil between changes.  Sorry but I think the problem is somewhere else.

Ugh, I was hoping for an easy solution; back to the dart board.  Someone else sent me a picture of a Rocket in which the breather terminated well inside the cowl flap.  Maybe I'll cut mine back a bit; it's as good of science as anything else at this point.  Thanks for the feedback!

[snowds]

On my IO-360 the breather has a small hole a few inches above the end of the tube. It was explained to me that it was there to prevent a siphoning effect from air passing the end of the tube. Do your tubes have this as well?

There was a small anti-siphoning hole in the line (or some would call it an ice hole), but we put in a much larger one.  This definitely cut the oil back quite a bit, but it is still more than it should be.

[Awful_Charlie]

Check out the 'Whistle Slot' chapter in http://www.7ts0.com/manuals/lycoming/Lycoming_SB_SL/flyer/Lycoming%20Flyer%20Key%20ReprintsGENERAL.htm - it's there in case the end freezes over

[aviatoreb]

Ugh, I was hoping for an easy solution; back to the dart board.  Someone else sent me a picture of a Rocket in which the breather terminated well inside the cowl flap.  Maybe I'll cut mine back a bit; it's as good of science as anything else at this point.  Thanks for the feedback!

 

I would definitely call the company Rocket Engineering if you have not already.  They have provided excellent service to their fleet.

[RocketAviator]

Here is a shot of my Rocket breather tube.. Let us know what you find out.

Bt the way what is the black hose zip tied to your breather tube?

[davidsguerra]

Mine did this until i got an Airwolf oil/air separator and stopped climbing at 1600 fpm every flight. not a drop since.  the original oil air separator is meant for a 4 cylinder.  it did take some adjusting to get it perfect though.  Phil Jimenez did the work and can probably talk you through the pitfalls. many dissuaded me from getting it but it fixed the problem.

[David Mazer]

I thought about an oil separator too but after my engine was rebuilt there wasn't any oil leakage to separate.  Makes me wonder if you are covering up a problem rather than solving it.

[jasonwojo]

Just sent you a PM...

[snowds]

Here is a shot of my Rocket breather tube.. Let us know what you find out.

Bt the way what is the black hose zip tied to your breather tube?

I'm not quite sure what the two hoses are tied to the breather; they are the same as the two on yours that terminate just prior to your 90 degree turn.  I think the mechanic told me at one point that one goes to the fuel pump, but again, I'm not certain.

 

The driest the belly has ever been was right after the shaft seal was swapped, about 300 hours ago.  Maybe it's getting time for a new shaft seal again.

 

Very frustrating issue.

[aviatoreb]

I'm not quite sure what the two hoses are tied to the breather; they are the same as the two on yours that terminate just prior to your 90 degree turn.  I think the mechanic told me at one point that one goes to the fuel pump, but again, I'm not certain.

 

The driest the belly has ever been was right after the shaft seal was swapped, about 300 hours ago.  Maybe it's getting time for a new shaft seal again.

 

Very frustrating issue.

 

Snowds, this sounds like a real problem that is out of speck with what should be going on.  Please heed this as a warning of something potentially much more serious than simply a messy under belly.  Your engine is speaking, its screaming, so please listen.

If I were in your position and my mechanic could not solve it I would seek a second opinion.  Have you considered visiting one of the half dozen most experienced MSC's?  Have you spoken to the company that still supports the Mooney Rocket wonderfully, Rocket Engineering?

[RocketAviator]

Here is a shot of my Rocket breather tube.. Let us know what you find out.

Bt the way what is the black hose zip tied to your breather tube?

Anyone else notice MY loose screw in this photo... after I saw this I climbed under my ol bucket of bolts and checked and tightened everything I could find!!  

[davidsguerra]

I thought about an oil separator too but after my engine was rebuilt there wasn't any oil leakage to separate.  Makes me wonder if you are covering up a problem rather than solving it.

Phil had my engine almost full throttle  with the cowling off several times with no leaks.  it would always leak new oil out of the breather tube, worse on  prolonged  1600 fpm climbs.  havent lost much oil since the oil/air seperator.  the Airwolf is like 3 times bigger than the original which was meant for a four cylinder.   hangar is clean and and i am happy.

[floridaflyer]

Snowds I'm reviving this post in the hope you found a fix. My 87 Rocket 305 has the exact same symptoms as you described in your original post. The most frustrating part is No predictability with no warning on long flights and related safety issue. All comps good, no oil on plugs, waiting on used airspeed indicator to do the crankcase pressure test, Air wolf 311E  Air separator on order. Any resolution appreciated. 

[peevee]

35 minutes ago, floridaflyer said:

Snowds I'm reviving this post in the hope you found a fix. My 87 Rocket 305 has the exact same symptoms as you described in your original post. The most frustrating part is No predictability with no warning on long flights and related safety issue. All comps good, no oil on plugs, waiting on used airspeed indicator to do the crankcase pressure test, Air wolf 311E  Air separator on order. Any resolution appreciated. 

He hasn't been here in over a year, might try sending a pm or email if it allows. Sorry about your troubles 

[floridaflyer]

2 minutes ago, peevee said:

He hasn't been here in over a year, might try sending a pm or email if it allows. Sorry about your troubles 

Thank you for the heads up. 

[carusoam]

Try this... @snowds this will light a red light at the top of his MS viewer....

His page says he visited MS a few hours ago...  he just hasn't posted anything in years...

If you click the like button on his post, he will get a notification of that as well...

Many of us don't want to write very much.  

Best regards,

-a-

Edited June 20, 2017 by carusoam

[peevee]

He probably visited because he got an email notification. He hadn't in over a year 6 hours ago.

[Piloto]

Try a single grade oil like W100. Crankcase pressure is due to hot air leakage through the piston rings during the power stroke. High oil temperature compounds the problem by  making the oil thinner (more leakage) and higher oil vapor formation. Oil separators are a good solution that besides keeping the belly clean it keeps from losing oil. I have an M20 oil separator and very happy with it. Check oil temperature during climb. Most of the oil is lost during a prolonged climb so try to keep a low CHT. BTW icing of the breather tube is very rare since the oil vapor temp is at least 140F.

José

Edited June 21, 2017 by Piloto

[floridaflyer]

40 minutes ago, Piloto said:

Try a single grade oil like W100. Crankcase pressure is due to hot air leakage through the piston rings during the power stroke. High oil temperature compounds the problem by  making the oil thinner (more leakage) and higher oil vapor formation. Oil separators are a good solution that besides keeping the belly clean it keeps from losing oil. I have an M20 oil separator and very happy with it. Check oil temperature during climb. Most of the oil is lost during a prolonged climb so try to keep a low CHT. BTW icing of the breather tube is very rare since the oil vapor temp is at least 140F.

José

Thanks Jose. I'm already using 100W oil and according to engine monitor oil temp stays below 200F during climb. I ordered an AIrwolf separator, unless and until leakdown + borescope says otherwise, oil won't have any other way to go but back in crankcase...