O470R

[LesGawlik]

Cessna 182 with O470. There is an oil breather tube at the top front of the engine. It is a capped tube about 1 1/4" diameter. There is another tube at 90* about 3/4" diameter intersecting the main breather tube. It is to this 3/4" tube that rubber tubing is routed to the air/oil separator.

At one time, it looks like someone wrenched on the larger, vertical tube. We see marks that look like Vise Grips or gas pipe pliers were used to grab the tube. The joint between the larger, vertical tube and the smaller horizontal tube has cracked and is apparently allowing oil vapor to escape. Then it looks like someone tried to braze the joint, but that didn't work. Then, the Handyman's Friend, JB Weld. Needless to say, it still leaks.

There is very little oil that leaks from the breather tube. But it exits the cowl and blows back on the windshield. Again, not a major problem, except that at night the mist interferes with vision.

I don't see this as something which will lead to significant oil loss. It is a few milliliters per hour. The oil breather is not under significant pressure, and it handles oil vapor. There is no oil aft of the breather. The engine is completely dry. There is no oil at the base of the breather. There is a trace of oil on the front of the engine, below where the vapor would exit the cowl.

The problem is that breather is, I'm told, pressed in. It cannot be replaced as a field repair.

Here are the ideas.

-Clean it up and redo the joint with a hitemp sealer.

-Get a new breather and cut off the top 2". Cut the existing breather tube off and
-TIG the two together
-Use a short section of neoprene tube to join the old breather stub protruding from the case and the new section of breather tube containing the 90* junction

Any ideas?

I am frankly astonished that air could be pulled out of cowl and flow up to and over the windshield. I figured between forward speed and prop blast would make the airflow into the cowl, and only into the cowl. But if you look carefully at the front of the cowl on the pilot's side, there is a trace of oil vapor, and of course, there is mist on the pilot's side of the windshield.

I'm wondering if has anything to do with prop pitch. Perhaps when going to flat pitch, a relative low pressure area is created on top of the engine, and the vapor is sucked out and blow across the top of the cowl.

 

[Wagondriver]

Are you sure that is where the oil on the windshield is coming from? A leaking prop hub will do that too. I'm no mechanic, but all the breathers you describe go down behind the engine to the bottom of the firewall, not to an air oil separator.

As a quick interim fix, I'd clean it up real good and use RTV silicone liberally over the crack.

 

[LesGawlik]

I am almost sure that it is from the breather, and not the prop hub. First, the mist is not evenly distributed across the top of the cowl, it is confined to the left or pilot's side of the cowl, exactly above the breather. The mist on the windshield is not distributed evenly, it is concentrated on the left side of the windshield, in line with the breather and the mist on the cowl.

This breather is on the top of the engine, in the front. A neoprene tube runs across the top of the engine to the rear baffle. The air oil separator is mounted high up on the back of the baffle, on the pilot's side. Pretty sure it is a breather.

 

[455 Bravo Uniform]

Dude, you can’t go straight to a proper fix without putting duct tape on it, at least for a touch & go?! What kind of owner/pilot are ya?!

 

[Bell206]

Any ideas?

While I can't picture the tube you reference at my current location, I have stopped leaks at engine case breather fittings with Proseal 890 sealant. It requires extensive prep of the leak area to work but have had a good success rate. As to welding on an installed engine, while it has been done... not a good idea.

 

[LesGawlik]

I think I may go with the Proseal. I know part of the problem is that there is some slag on the smaller tube from the brazing operation. So the neoprene hose cannot make perfect contact with the nipple portion of the breather assembly. I think a file or a little sandpaper would smooth those bumps out, and allow a better fit between the nipple and the hose.

 

[LesGawlik]

This is the breather. It is leaking between the vertical tube and the horizontal hose nipple. Is this pressed in? Can it be replaced in the field, and if so, how?

 

[Bell206]

Is this pressed in? Can it be replaced in the field, and if so, how?

I believe some are pressed and some are screwed in. But a quick call to the TCM support (or a shop) will get you the proper answers.

 

[LesGawlik]

I thought I would update this thread with my recent activities.

First, I have eliminated the problem. Second, learned that during some portions of the flight, air can flow forward out of the front of the cowl, flow across the top of the cowl and up to the windscreen. I never thought that would be possible, given the prop blast and the speed of the airflow in flight. (Maybe it was while cycling the prop during runup? Maybe going from coarse pitch back to fine created a momentary low pressure area in front of the engine?)

I also concluded I was losing more oil that I thought. While the oil on the windshield was minor, the breather was of course leaking all of the time. The oil vapor apparently went over the cylinders and out on the belly, which was always dirty.

I took a very small wire wheel on a die grinder to clean up the fitting, and blocked off vent. I mixed some ProSeal and used a vacuum cleaner attached to the oil filler to create negative pressure in the crankcase. My hope was that the vacuum would draw some sealant into the cracks or porosities in the brazing of the breather. I applied a little heat to help with the cure, but it still a few days to set up because of the cold temperature.

Several flights later the breather is dry, the upper lip of the cowl is dry and there is no oil on the windscreen.