Engine venting after shut down, what ya think?

Used to do that with my Mooney. Not sure it helped, but didn't think it could hurt.
 
I've been preaching that for years, where have these guys been?
 
Good lord, I started taking the oil filler cap off on shut-down as soon as I put the plane in a hangar. This is not a rocket science thing...
 
I do it every time I fly. You can't imagine the amount of "steam" (water vapor) that comes out of the crank case as a by product of combustion. Each gallon of gas burned produces 1.2 gallons of water. Some gets into the crank case through blow-by. This is why is it critical to get you oil temps up to 200F+ every flight to boil off the water from the last flight.
 
If you got the time sure, not sure how large of my difference it's going to make though, just be sure not to forget to button her back up.
 
It won't work on small Continentals. Their oil filler necks are low enough on the tank that the only oil exposed to the air with the cap off is a small circle, not the whole oil surface or crankcase. The only way out for vapors in those engines is the crankcase breather.

My oil tank is like that. It is 69 years old and it's not rusty from moisture. On the other hand, the inside of the rocker covers get rusty, like most do.
 
Geico266 said:
I do it every time I fly. You can't imagine the amount of "steam" (water vapor) that comes out of the crank case as a by product of combustion. Each gallon of gas burned produces 1.2 gallons of water. Some gets into the crank case through blow-by. This is why is it critical to get you oil temps up to 200F+ every flight to boil off the water from the last flight.
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I learned a slightly different method when I got the Waco. A friend who is a long time Stearman owner and restorer told me to get a small air mattress pump and hook it up to the crankcase breather tube and suck the air out when done flying. You do see some water vapor come out.

The Continental W-670 never gets the oil anywhere close to 200F. Even in the summer at max cruise I don't think I've seen he oil temp get above 160F.
 
Dan Thomas said:
It won't work on small Continentals. Their oil filler necks are low enough on the tank that the only oil exposed to the air with the cap off is a small circle, not the whole oil surface or crankcase. The only way out for vapors in those engines is the crankcase breather.

My oil tank is like that. It is 69 years old and it's not rusty from moisture. On the other hand, the inside of the rocker covers get rusty, like most do.
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Every Continental smaller than the 0-200 has a kidney tank behind and below the crankcase. with the filler neck in the top right side.

Pull it off you'll get steam.
 
Fearless Tower said:
I learned a slightly different method when I got the Waco. A friend who is a long time Stearman owner and restorer told me to get a small air mattress pump and hook it up to the crankcase breather tube and suck the air out when done flying. You do see some water vapor come out.

The Continental W-670 never gets the oil anywhere close to 200F. Even in the summer at max cruise I don't think I've seen he oil temp get above 160F.
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Isn't it weird? they lasted this long with out any one worrying about ?
 
James331 said:
If you got the time sure, not sure how large of my difference it's going to make though, just be sure not to forget to button her back up.
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Do you normally check the oil before you go fly? do you put it back then?

Why does it matter if it is left off until then?
 
Tom-D said:
Do you normally check the oil before you go fly? do you put it back then?



Why does it matter if it is left off until then?
Click to expand...


Bugs? Mice?




Sent from my iPhone using Tapatalk
 
Tom-D said:
Every Continental smaller than the 0-200 has a kidney tank behind and below the crankcase. with the filler neck in the top right side.

Pull it off you'll get steam.
Click to expand...

Top right? With these tanks the oil is up inside the filler neck when full.



$_35.JPG
 
I understand it makes you feel good, being proactive about water vapor inside the engine, but, oil is hygroscopic, meaning it can absorb moisture directly from the air. When the engine is sitting idle (not running) the oil is absorbing moisture.
 
Tom-D said:
That article is a real snoozer.
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Really? You didn't think this was interesting? It also relates to two other threads here.

"Manufacturers recommend that the new engine break-in be done with a mineral-based oil rather than an ashless dispersant oil. This process creates a varnish-type coating on the metal parts that will protect the metal from rust. The break-in period is normally considered about 50 hours."
 
Tom-D said:
Do you normally check the oil before you go fly? do you put it back then?

Why does it matter if it is left off until then?
Click to expand...

Misc crap getting in there, or rain, that would defeat the whole point rather quickly
 
I guess I split the difference. I always pop the cover over the dipstick on the Cherokee 180 to let the heat more easily escape, but I don't pull out the dipstick. My original reason for not opening up the dipstick was because I didn't want to assume that the other partners in the flying club always checked the oil. Yeah, I know, everyone had BETTER be doing this, but...
 
My crankcase IS vented. The article says trapped steam will evaporate and cause corrosion? Did a third grader write that? There is moisture inside a hot engine, no doubt. Does opening the oil cap reduce the moisture? Maybe, but the introduction of fresh, cool air introduces new moisture. Assuming there's moisture in there either way, whether venting reduces it or not? The response to manage corrosion by the owner is the same. Fly often, assure oil temps get hot enough to boil out moisture, change oil often, add your favorite anti-corrosion elixir.... Opening the oil cap doesn't solve anything.
 
GlennAB1 said:
I understand it makes you feel good, being proactive about water vapor inside the engine, but, oil is hygroscopic, meaning it can absorb moisture directly from the air. When the engine is sitting idle (not running) the oil is absorbing moisture.
Click to expand...

It might be, it might not be. When I pull the filler cap off after a flight, there will frequently be a visible emulsion (oil & water) coating some of the surfaces of the filler cap. After a day or so the visible emulsion will be gone.

The first time I saw the emulsion, I ask an A&P if that was normal and the reply was that all piston aircraft engines were that way. At first I thought about coatings to protect the metal but then stumbled on the very simple step of simply leaving the filler cap off. Of course this solution isn't any good unless the aircraft is in a hangar. I also loosely cover the filler neck with a rag to keep dust and insects out. The rag also covers the filler cap to keep dust off of it.

My A&P has adopted the practice...

One thing to note, I live in a very dry climate. Things may be different in humid areas.
 
Tom-D said:
Do you normally check the oil before you go fly? do you put it back then?

Why does it matter if it is left off until then?
Click to expand...

That was my first take on it. Do you ALWAYS check under the hood, even if you've just been on the ground for a little while. Just takes one dogooder to close the hatch for you and you forgot you left the oil cap open.
 
I can't get my filler cap off without pliers so I'm not doing this. The only way that doesn't happen is if I leave it so loose that it makes me nervous. I don't even tighten it that hard but after a flight that damn thing is ON there, brother.
 
Tom-D said:
Isn't it weird? they lasted this long with out any one worrying about ?
Click to expand...
Perhaps, but you also need to consider that these engines were getting a heck of a lot more regular usage back then. I'd imagine that a Stearman in the '40s was flying easily 50 hrs a month and probably more.

Today, most of these engines are lucky to get 50 hours a year.
 
I'm really surprised Kent hasn't chimed in yet. He's a big advocate of pulling the filler cap immediately after shut down.
 
I've done it a time or two after a long flight and stuff comes out but it's a pain in the ass that I don't think is worth the extra 5 hours of engine life you MAY get.

The mother-trucking oil cap is hot and you gotta stand up on the main tire and balance your ass....

I'm getting too old for this s...


flat,1000x1000,075,f.u3.jpg
 
petrolero said:
I can't get my filler cap off without pliers so I'm not doing this. The only way that doesn't happen is if I leave it so loose that it makes me nervous. I don't even tighten it that hard but after a flight that damn thing is ON there, brother.
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Wrong O-ring on the cap.
 
Another reason for positive crankcase ventilation - especially just prior to engine shutdown. I understand this is why newer car engines last so long.
 
nrpetersen said:
Another reason for positive crankcase ventilation - especially just prior to engine shutdown. I understand this is why newer car engines last so long.
Click to expand...

But it won't work with aircraft engines. It requires relatively low manifold pressure to suck air through the crankcase, and aircraft engines are usually working at high power settings where the MP is too close to ambient to make it work. And the large clearances found in air-cooled engines cause more blowby gases and oil mist that would very quickly gum up the PCV valve. A stuck valve could be disastrous.
 
Geico266 said:
I do it every time I fly. You can't imagine the amount of "steam" (water vapor) that comes out of the crank case as a by product of combustion. Each gallon of gas burned produces 1.2 gallons of water. Some gets into the crank case through blow-by. This is why is it critical to get you oil temps up to 200F+ every flight to boil off the water from the last flight.
Click to expand...

You may be 100% right, but I'd like to see the math on that. I remember way back when learning about some law having to do with conservation of mass, written by some old dude.
 
Blatham489 said:
You may be 100% right, but I'd like to see the math on that. I remember way back when learning about some law having to do with conservation of mass, written by some old dude.
Click to expand...

Do you need someone to google that for you? Or jus' slap you and make some snide remark about oxygen?
 
Clark1961 said:
Do you need someone to google that for you? Or jus' slap you and make some snide remark about oxygen?
Click to expand...

Upon further reflection and investigation, I'll take the slap and snide comment please.

Been even longer since I took chemistry apparently.Hoist on my own petard.
 
Blatham489 said:
Upon further reflection and investigation, I'll take the slap and snide comment please.
Click to expand...

WHAP! Maybe if you'd breath a little bit you'd get some OXYGEN to yer brain...!

Was that enough? :D
 
Dan Thomas said:
Wrong O-ring on the cap.
Click to expand...

It's doubt it's a sticky O-ring that's holding it on there but I'll check that.

It seems like metal expansion and contraction. I can put it on loose and it will become tight as **** as I fly it.
 
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