Breather tube termination/exit

flyingfool · Post by **flyingfool** » Mon Aug 25, 2008 10:34

Where should the breather tube terminate?

Specifically, my breather tube terminates about 4 inches above the exit of the cowl on my A-65 Chief. Someone told me that the tube should extend to outside the cowl. The theory was that with the termination where it is on my plane, it is in an area of vaccum (low pressure) and that vacuum will actually suck more oil from the breather. However if I extended this tube to outside the cowl and along the bottom of the airplane facing rearward, I don't see how this would not also cause suction

2 Further questions.

1) If I did extend this tube, how far below the cowling should it be? OR does it matter. And how do I attache the extended tube to the unerside of the plane?

2) I know I have to have a "whistler" hole in the breather and that must be located inside the cowling. How big dies this hole need to be?

MikeB · Post by **MikeB** » Mon Aug 25, 2008 12:26

For whatever it's worth, I have a extension on the breather for my 7AC that is about 2 inches below the cowl exit. I just safety wired it in place. Doesn't seem to bother regarding sucking oil with with the breather fumes but it does keep my cowl cleaner inside.

However, when the weather gets cold you want the breather tube up inside the cowl so the breather doesn't ice up and build pressure which will cause all kinds of blown gaskets and seals.

The whistle hole on mine is in the breather hose just below the breather elbow. Probably 1/8 or so in size, but not exactly sure.

Mike Berg

gusc · Post by **gusc** » Mon Aug 25, 2008 23:36

I did a lot of research and experimenting on my Navion with this sugject since I was coating the belly with anit-corrosion fluid!

After reading about a C-180 losing all his oil in a matter of minutes when he extended the vapor line well out into the slipstream I decided I definitely wouldn't do that since it was the same engine type!

Having said that it may be that with 65hp the speed isn't great enough to suck out any oil anyway??

I don't buy the theory that there is more suction inside the cowling than in the slipstream.

Even with a tube extended the oil will probably end up on the tail fabric anyway. It is better on the metal cowl in my opinion.

If yours isn't making a big mess I wouldn't fool with success. My 7AC tube exits at about the same level as yours.

If you want to experiment you could start with a long rubber tube and keep cutting it off untill you find the optimal length. If you do, let us know the results!!

My tube is rubber. I think rubber is better than metal in cold weather. I'm not even sure that a hole is necessary in our southern climate.

flyingfool · Post by **flyingfool** » Tue Aug 26, 2008 09:09

My breather tube is rubber from the elbow out of the engine. It then goes down and about half way it changes to aluminum tube which is clamped to the engine mount in various places and the aluminum tube is bent down and terminates I'd guess about 4 inches or so above the cowl opening. It does NOT drip on the cowl when sitting in teh hangar. Rather it drips straight down and onto the floor and onto a now awaiting peice of cardboard.

I have not looked for the whistler hole.

I think I will see how this goes for a while. If I don't like the oil mess, I will extend the breather tube a little bit. Maybe at a couple inches at a time. Start with 2" then remove and add 4" etc.

I've heard that Cub owners extend the tube to down by or aft of their main landing gear bungees.

Does this tube extension have to be anything FAA approved, or can I just go down to the hardware store and get some of that clear plastic tubing and hose clamp it on?

Does the whistler hole have to be in any special location or can it be virtually anywhere along the tube?

big chief 48 · Post by **big chief 48** » Tue Aug 26, 2008 09:40

Hi.. I'm from northern MN, and the breather tube is really important up here in the cold. I've had the best results by having the rubber tube exit at the curve of the cowl opening. There is no way oil will be "sucked"out if it is longer. As far as the whistler hole is concerned, 1/8 to 1/4 is fine. Up here they are a little larger due to the really cold weather -10 to -25 F. One thing of importance is where you put the hole. The old timers up here have them cut out 16-24 inches from the elbow. Too close and it blows oil vapor all over. Put the cut on the outside of the bend!!!! I found out if it is on the inside, the oil vapor can condense, run down the side of the tube and exit through the cut, making quite the mess.. Hope this helps.

flyingfool · Post by **flyingfool** » Wed Aug 27, 2008 09:36

I live in WI so it gets plenty cold in the winter. I plan to choose my days wisely when I fly in the winter. So it will probably be sunny and maybe 25 degrees or warmer. When it is colder than that, I'll spend time next to the fire and my kids....or on the internet doing some hangar flying!

So is the freeze up protection whistler hole a drilled hole, or a slit? Or doesn't it matter?

Because mine is an aluminum tube, if it does not already have a hole, I was thinking of just drilling a 1/8" hole in the aluminum tube on the top of the tube so any condensation and oil drippngs will not drip out through the hole.

Would this work? is 1/8" large enough?

Nathan K. Hammond · Post by **Nathan K. Hammond** » Wed Aug 27, 2008 22:40

1/8" is just a bit small; 1/4 would be better. Yes, put it on top of the tube. Ideally, the whistler hole is somethere in a *warmer* part of the cowl i.e. no direct wind blowing on it.

Each airplane is different; some like the breather out 4", others flush, my Champ liked it inside the cowl. So don't be surprised if it gets worse. The other thing to try is re-routing the breather line over the cylinders, through the rear baffel and then down the back side of the engine. This makes any oil travel up-hill before being blown out; it helped mine stay cleaner. Place the whistler just behind the rear baffel where it is less likely to freeze.

nkh

flyingfool · Post by **flyingfool** » Thu Aug 28, 2008 09:46

My breather goes straight down and through the baffle directly after leaving the case. It then angles downward and back on at varying angles until the rear of the engine, and then it steepens to a much steeper angle downward. It terminates like I said about 4 inches above the bottom of the cowl opening and about mid way between firewall and forward cowl opening.

I don't seem to have a problem with oil on belly. In fact the breather only drops a few drips on to the hangar floor after flying.

I just want to locate and ensure or install a whistler hole. At this point I have not seen it or felt it. So I'm a bit suspicious that there is one on my plane, but it is completely possible that I just have not located it.

With this angled arangement, I'll have to try to figure a place to drill a hole if one isn't already there.

gusc · Post by **gusc** » Thu Aug 28, 2008 23:45

Mine is all rubber from the crankcase elbow to the bottom of the firewall. It is right up against the firewall and ends just above the boot cowl that protudes about an inch past the firewall where the removable bottom cowling connects.

There is no oil anywhere that I can see so it stays put.

If it ever starts blowing oil I'll reverse the crankcase elbow and run it above the engine like Nathan says, this is actually the method the big Continentals use.

My theory is that rubber is best in cold climates somply because rubber is not a very good heat conducter and thus shouldn't freeze oil vapor as much. Of course this is only my theory.