Crankcase Breather Tube Position for a ‘66 E

[Yourpilotincommand]

I suspect mine is not in the correct position and maybe pulling a suction drawing out excessive oil vapors from the crankcase… and on to the belly. It’s an easy check to eliminate the cause of my excessive oil consumption.  Would someone kindly share a picture of their tube and a measurement? I’ll photograph mine next time I’m at the hangar. I’m hoping that’s the issue.  I do have chrome cylinders which are known to have a higher blow-by than other types. I’ve been consuming about a quart very 4ish hours and would like to improve that. I am also considering a AOS. Also.. my oil filler tube is always loose at the base and seems I have to tighten it each flight.. I understand the loose filler tube could be a cause of elevated crankcase pressure. I might do the old airspeed indicator trick to check the crankcase pressures as Mike Busch mentions. Comments please! Thanks, Chris

here is a great video from Mike Busch discussing crank case pressures, blow by, leaks, causes, etc…. 

 

[mike20papa]

Where the hose connects to the alumn. tube at the cowling bottom .. make sure that the hose is not covering a hole about the size of a #10 drill.

[carusoam]

There is a discussion about the whistle hole and it’s location around here somewhere… including all the details about location and length…

I think @GEE-BEE AEROPRODUCTS offered to make nice replacement parts for it…

Doc probably supplied maintenance manual drawings…

Chrome cylinders are known for not breaking in very easily… resulting in higher oil use/loss…

 

PP thoughts only, not a mechanic…

-a-

[Yourpilotincommand]

Any opinions on the placement of the breather tube? The red arrow in the 2nd photo notes the “whistle hole”.  The blue arrow notes the position of the tube end above the bottom of the fuselage at firewall which is approximately 1 inch. Wondering if it needs to be flush. Thanks.

 

 

[carusoam]

The dimensions are there for a reason….

Mostly, it took somebody a long time to figure out why stuff didn’t work…..

When it comes to vent tubes in an airstream… they want to avoid vacuums, pressurization, or stay about neutral…

Simply find the dimensions, and install that way….

Expect that some tubes got replaced, and didn’t get executed properly, or something changed….

Best regards,

-a-

 

[Yourpilotincommand]

9 hours ago, carusoam said:

The dimensions are there for a reason….

Mostly, it took somebody a long time to figure out why stuff didn’t work…..

When it comes to vent tubes in an airstream… they want to avoid vacuums, pressurization, or stay about neutral…

Simply find the dimensions, and install that way….

Expect that some tubes got replaced, and didn’t get executed properly, or something changed….

Best regards,

-a-

 

Thanks Carusoam. That’s my problem... I cannot find the dimensions.

[47U]

On 1/13/2022 at 1:39 PM, Yourpilotincommand said:

I suspect mine is not in the correct position

Found this thread on a Bing search… 

 

[carusoam]

Bob Belleville did a nice job showing where the hose is located… but, his installation was updated after that pic… (to include the whistle hole in a metal tube….

Let’s see if @M20Doc can give insight on the length of the case vent extension… (how far below the sheet metal the tube extends?)

Best regards,

-a-

[jamesm]

I have been experimenting with mine. I want to see if  increasing the length that is  expose out in the slip stream will keep the oil off the belly.

[asaxet]

what level are you servicing the sump to....   On my 66e anything more than 5 quarts showing on the dip stick ends up on the belly in short order....      

[Guest]

There seems to be a number of different shapes for the aluminum tube portion of the vent system.  It would be best to check with tech support at Mooney to get the correct shape and size tube.

Clarence 

[Yourpilotincommand]

Thank you Carousam and 47U !!! I at least know that my breather tube is upside down (whistle hole) as well as out of position.  

[Prior owner]

Before I go into my experience, what oil level are you starting your consumption measurement from? Try filling oil to 5.5 - 6 qts only, put 4 hours on it, then check it the next day when it’s cold- did you really lose a full quart? If you’re starting at 7 quarts, you’re not doing yourself any favors.
 

I too, had issues with my channel chrome cylinders… compressions were good, engine power seemed fine, my oil consumption was a little bit worse than yours, and I spent a good deal of time researching the issue, worrying about it, manipulating my vent tube placement, making a whistle hole, eventually installing an Airwolf oil/air separator, and finally, removing the separator.

The fact is, you have chrome cylinders…and like many of the owners who do, you’re never going to enjoy the ridiculously low oil consumption numbers that you sometimes read in this forum. Provided you don’t have any other cylinder health issues and you aren’t exceeding the oil consumption limits In Lycoming’s manual, chrome doesn’t have to be a bad thing.

For $600+ An oil/air separator will keep your belly clean and might even give you another 0.25 to 0.5 hours more per quart, but you’ll be feeding combustion byproduct  acids right back into your engine- I’ve cleaned too many of these things out, and they just don’t completely separate ALL the acids and water from the oil…. A breather vent pipe accomplishes this task much better.

In my limited experience, I would say, have the engine inspected and assessed properly, so that you can stop worrying about it, and feed the beast oil while you enjoy your plane for years to come… or, buy 4 new cylinders and be done with it.

The maintenance history on my cylinders was poorly documented, and although my engine was only about 65 hours out of overhaul when I bought the plane, from what I could gather, the chrome cylinders had 200+ hours on them, and my borescope revealed that someone (overhaul shop?) had run a hone through all of them (which is a no-no), and they were all glazed. My oil temp was also elevated due to excessive cylinder blowby. I wasn’t going to put another hour of my time or another dollar into attempts to de-glaze & re-ring chrome cylinders that had been damaged with a hone…so I installed 4 new  cylinders.

My Tailpipe is now dry, my breather drips a few drops on the ground at the end of each flight, and oil consumption is much better. 

You might be in a different situation as far as the condition of your cylinders- a qualified A&P with a borescope should be able to properly assess your situation. 

Here’s one cylinder at roughly 100 hours SMOH and its intake valve (all the cylinders were in about the same condition)- obviously, I had more issues than just glazed cylinders:

[N6066Q]

@Yourpilotincommand can you kindly take a picture of how your breather tube looks now and post? Did your adjustments have a tangible impact to oil useage? Thanks in advance.