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Sniffle Valve Waste

Mark Dickens

Well Known Member
Patron
I have the Lycoming sniffle valve installed with a AFP injector. When I shut the engine down, even after running it very lean prior to shutdown, I get a small puddle of gas/oil mix. Since I don't yet have this plumbed anywhere, it drips on the inside of the cowl and runs down to the edge of the cowl and then onto the floor. This is an unacceptable mess.

I want to keep the sniffle valve through at least the phase one period, so I have to figure out what to do with the waste. I was wondering if anyone had plumbed this to a small holding container like a gascolator that could be drained before each flight....having to put a cookie sheet under the plane as if it was a T-6 just doesn't seem right to me, yet I do want to have the protection of the sniffle valve. What say ye?
 
Route it into a mason jar and put it in your lawn mower..... ;)

Small motors love avgas and it doesn't go off like auto gas does.
 
Gas/oil mix?
That doesn't sound right, or good. There should not be ANY oil in the sniffle valve output, only fuel that boils out of the injection lines, re-condenses in the intake chambers and drains down the intake air pipes into the manifold.

I get just a few drops out of my sniffle valve. It is routed thru a tube that drips it out behind the cowl. It doesn't even drip enough to make a puddle, it just evaporates.

The only reason I can think of that you would get oil there would be a badly leaking valve guide on an intake valve, allowing oil to leak into the intake chamber of the cylinder head.
 
Gas/oil mix?
That doesn't sound right, or good. There should not be ANY oil in the sniffle valve output, only fuel that boils out of the injection lines, re-condenses in the intake chambers and drains down the intake air pipes into the manifold.

I get just a few drops out of my sniffle valve. It is routed thru a tube that drips it out behind the cowl. It doesn't even drip enough to make a puddle, it just evaporates.

The only reason I can think of that you would get oil there would be a badly leaking valve guide on an intake valve, allowing oil to leak into the intake chamber of the cylinder head.

True, except this is a new engine, and sometimes during the first few runs there is oil and or preservation lubricants in the intake area that has run down there during the period of inactivity. It should go away over time.

Vic
 
Gas/oil mix?
That doesn't sound right, or good. There should not be ANY oil in the sniffle valve output, only fuel that boils out of the injection lines, re-condenses in the intake chambers and drains down the intake air pipes into the manifold.

I get just a few drops out of my sniffle valve. It is routed thru a tube that drips it out behind the cowl. It doesn't even drip enough to make a puddle, it just evaporates.

The only reason I can think of that you would get oil there would be a badly leaking valve guide on an intake valve, allowing oil to leak into the intake chamber of the cylinder head.

I get the same thing on my engine and it has been nearly 590 hours on it and still the same. Numerous calls and discussion with Lycoming, they have assured me that is of no concern, I have certainly have not had any issues. I am still baffled as how the oil gets in there, only suspect around the intake valve guide.
 
Whatever the waste is composed of, it's some mix of gas and oil. Color is a blackish-green...I have an AFP injector and from what I read they do let some fuel through at shutdown. With maybe 6 hours on a new engine, I'm not ready to pull it off and send it in for a top overhaul yet :rolleyes:

My question was what to do with the waste...I can't use it in my lawnmower, because I haven't owned one for several years (who has time to mow AND build?)

Any input on the gascolator idea?????:confused:
 
True, except this is a new engine, and sometimes during the first few runs there is oil and or preservation lubricants in the intake area that has run down there during the period of inactivity. It should go away over time.

Vic

Hope that's all it is.
 
I get the same thing on my engine and it has been nearly 590 hours on it and still the same. Numerous calls and discussion with Lycoming, they have assured me that is of no concern, I have certainly have not had any issues. I am still baffled as how the oil gets in there, only suspect around the intake valve guide.

You're not the only one. A good thread on this subject: http://www.vansairforce.com/community/showthread.php?t=123858
 
Any input on the gascolator idea?????:confused:

I used to own a Dodge diesel with a Cummins engine that had a similar factory installed system on the crankcase vent. It worked somewhat.:) It was basically a small plastic bottle that was vented and had a tube from the case routed through the lid. It still made a bit of a mess, as oily fumes from the bottle vent coated the surroundings and collected grime.

My 7's sniffle valve is connected to aluminum tubing via a short plastic hose. The tubing runs back to the firewall and is vented down at the firewall lower lip and through a drilled hole in the flange. I don't get much liquid out of it at all unless I flood the engine which is rare. Even then is it a small amount. I have the Silverhawk injection system.
 
Whatever the waste is composed of, it's some mix of gas and oil. Color is a blackish-green...I have an AFP injector and from what I read they do let some fuel through at shutdown. With maybe 6 hours on a new engine, I'm not ready to pull it off and send it in for a top overhaul yet :rolleyes:

My question was what to do with the waste...I can't use it in my lawnmower, because I haven't owned one for several years (who has time to mow AND build?)

Any input on the gascolator idea?????:confused:

Right at 200 hours on my IO360 with Bendix injection, same thing, I get maybe a dozen drops on hot shutdown, some mix of gas and oil, mostly gas judging from the viscosity as it drips out but enough oil to stain the concrete and color it.
 
My concern was when I'm not at the home hangar and it starts dripping but that's thinking too far ahead right now. I do need to see if this stabilizes at a smaller amount because there very well could be remnants of the preservative per Vic's comment. What I do need to do immediately is plumb it all so it's not dripping inside my nice new cowl. Maybe later I could set it up so that I could hang a small cup under the outlet to catch the waste rather than let it drip on a hangar floor or a tarmac...
 
My concern was when I'm not at the home hangar and it starts dripping but that's thinking too far ahead right now. I do need to see if this stabilizes at a smaller amount because there very well could be remnants of the preservative per Vic's comment. What I do need to do immediately is plumb it all so it's not dripping inside my nice new cowl. Maybe later I could set it up so that I could hang a small cup under the outlet to catch the waste rather than let it drip on a hangar floor or a tarmac...

Mark, I always attach a hose to the sniffle valve and route it aft out the cowling.

Vic
 
A short rubber hose from the sniffle valve to a length of .250 aluminum tube routed down to cowl exit, secured with an adel. You do not want to collect this fuel in a jar, you dont want it running down the cowl or fuselage, you want it going overboard. If you manage to flood the engine on a start or have some freak failure of the fuel system then it can move a bunch of fuel in a hurry. You dont want a full jar, cowl, or fuselage of fuel waiting to burn.

My advice is to get rid of the fuel, and live with the mess on the floor for a while until you get comfortable with what is going on.
 
Mine is extended via piece of aluminum tubing just to the exit area and I get 3-4 drops of mixture of oil/gas after each flight. I still curious for a good understanding as how the oil gets there. The pan that I have in the hanger to collect it shows very little amount of oil after all the gas gets evaporated
 
A short rubber hose from the sniffle valve to a length of .250 aluminum tube routed down to cowl exit, secured with an adel. You do not want to collect this fuel in a jar, you dont want it running down the cowl or fuselage, you want it going overboard. If you manage to flood the engine on a start or have some freak failure of the fuel system then it can move a bunch of fuel in a hurry. You dont want a full jar, cowl, or fuselage of fuel waiting to burn.

My advice is to get rid of the fuel, and live with the mess on the floor for a while until you get comfortable with what is going on.

Thank you for the best feedback so far...an excellent reason to NOT do what I was thinking about. I'll plumb it to the rear, let it drip on a drip tray of some sort and just watch it. Thanks to all, excellent thoughts!
 
Some of us simply eliminate the sniffle valve. Mine has gone 500 hours or so without it.

Took a look inside the Lycoming sump plenum last winter. I could get some fuel dye on a rag by wiping the plenum floor, but there was no buildup of any kind.

A sniffle isn't required in normal operation. It is an attempt to goof-proof the updraft sump, i.e. not allow enough liquid fuel to accumulate in the sump that a cylinder could suck up a big slug of liquid. Given a nosewheel airplane, that is unlikely, as the liquid fuel would merely run out through the throttle body. However, it could be a fire risk. A tailwheel RV might accumulate as much as a quart in a standard sump. Given the arrangement of intake pipes in standard Lyc sump, I doubt as much as a pint would affect anything.

What is the goof? Cold start prime...set mixture rich, full throttle, run the boost pump, and forget to turn it off. It's not just fuel. Builders who are running straight-in ram intakes may collect rainwater when parked.

I have a Lycoming sump, AFP with a purge valve (fuel can't leak into the engine after shutdown), and a large airbox with a rainwater drain. A different combination may get a different result.
 
Some of us simply eliminate the sniffle valve. Mine has gone 500 hours or so without it.

Took a look inside the Lycoming sump plenum last winter. I could get some fuel dye on a rag by wiping the plenum floor, but there was no buildup of any kind.

A sniffle isn't required in normal operation. It is an attempt to goof-proof the updraft sump, i.e. not allow enough liquid fuel to accumulate in the sump that a cylinder could suck up a big slug of liquid. Given a nosewheel airplane, that is unlikely, as the liquid fuel would merely run out through the throttle body. However, it could be a fire risk. A tailwheel RV might accumulate as much as a quart in a standard sump. Given the arrangement of intake pipes in standard Lyc sump, I doubt as much as a pint would affect anything.

What is the goof? Cold start prime...set mixture rich, full throttle, run the boost pump, and forget to turn it off. It's not just fuel. Builders who are running straight-in ram intakes may collect rainwater when parked.

I have a Lycoming sump, AFP with a purge valve (fuel can't leak into the engine after shutdown), and a large airbox with a rainwater drain. A different combination may get a different result.
I wish I had done the purge valve...
 
Sniffle valve drips

Hi Mark, did this ever stop dripping? Just curious - I've got a sniffle valve which drips from time to time.
 
After shutting down, I always get gas out of the sniffle valve for a little bit. I have a AFP injector without the purge line, so between the fact that ICO doesn't really cut off all the fuel and that last little bit of gas pumped by the mechanical pump, there's always some gas finding its way into the intake manifold.
 
Sniffle valve

After shutting down, I always get gas out of the sniffle valve for a little bit. I have a AFP injector without the purge line, so between the fact that ICO doesn't really cut off all the fuel and that last little bit of gas pumped by the mechanical pump, there's always some gas finding its way into the intake manifold.
Thanks Mark - I have the purge line, so I'll see if I can avoid drips using that and report back.
 
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