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Old 06-11-2017, 07:24 PM
Aussieflyer Aussieflyer is offline
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 55
Default Oil leaking from Sniffle Valve

My aircraft has now flown 110 hrs and I have changed my oil from
Mineral oil to Shell 100W 5 hours ago.
( Vans supplied IO-390 )

I am now getting oil dripping on the floor from the Sniffle Valve.
This is approximately the same amount I was getting when I tried to change from Mineral oil to 100W at 50 hrs, I was advised then to put the mineral oil back in and run for another 50 hrs.
Oil consumption while running on Mineral oil is approx 2 qts every 25 hrs and no dripping at all from Sniffle Valve.

Why does this happen when I change the oil ?

Can anyone advise what action I can take ?

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Old 06-11-2017, 07:38 PM
Bavafa Bavafa is online now
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 2,500

I am still getting oil (mixed with fuel) from my sniffle valve after 600+ hours. I bought my engine new from Lycoming and called them a number of times on this to understand it. At the end, they assured me that there is nothing wrong with the engine and ask to continue using it. They never asked me to change back to mineral. The engine has been running really great, no problem at all thus far.
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Phase one
Dues paid
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Old 06-11-2017, 07:41 PM
Ron B. Ron B. is offline
Join Date: Nov 2007
Location: Yarmouth, Nova Scotia
Posts: 2,238

Any chance it could be the valve itself?
Thanks Ron
RV-14 Flying
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Old 06-11-2017, 08:43 PM
vanduyn vanduyn is offline
Join Date: Aug 2006
Posts: 28
Default sniffel valve

I am seeing the same. A small amount of oil/fuel mixture after shutdown. Engine has 76 hours on the 390 and oil consumption is stable at 1qt every 10 hrs.
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Old 06-11-2017, 10:36 PM
KeithB KeithB is offline
Join Date: Mar 2014
Location: Granbury, TX
Posts: 182

Just another data point - I consistently get fuel drops from the sniffle valve. Sometimes just fuel, sometimes some oil mixed as well. Just switched to detergent oil (Aeroshell W100) at 60 hours - now at about 70 hours. I am using about a quart in 15-20 hours. Engine is a Superior XP400.
Keith Brown

RV-14A Builder - kit #136, XP-400 Aero Sport Power
N314KC - First flight Mar 8, 2017, >375 hrs
RV-6A sold
Sport Pilot (weight-shift control) - Airborne XT912
Dues paid 12/2018
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Old 06-12-2017, 05:32 AM
Mark Dickens's Avatar
Mark Dickens Mark Dickens is offline
Join Date: Apr 2012
Location: Collierville, TN (KFYE)
Posts: 1,037

For the first couple of engine runs after first start, I got a mixture of fuel and oil and since then, it's just been pure fuel after each shutdown.
RV-8 #81077 Super Slow Build
Titan IOX-370, Dual P-Mags, AFP FM200A FI, Sensenich GA Prop
First Flight 11/20/2016
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Old 06-12-2017, 10:35 AM
Bavafa Bavafa is online now
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 2,500

Just to add a bit more info that I add about a Qt. every 10 hours and has been consistent since the beginning.
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Phase one
Dues paid
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Old 06-12-2017, 06:34 PM
Wiley Wiley is offline
Join Date: Jul 2005
Location: Brownwood TX
Posts: 86
Default I had similar symptoms.

I have an injected M1B and did not place the sniffle valve. This past year I had persistent oil in the sump noted on scoping. If I had a sniffle valve, it would have been leaking similar to yours. I ended up finding a casting crack in the sump allowing a small amount of oil to trickle into the sump. It was more noticeable after switching to a thinner multiweight oil. Although this is an uncommon problem, remember it if you do not find any other cause.

This was written up in a different thread.

Good luck
Eric Wiley
RV-8 finished 9/15
Flying S Air Ranch (10XS)
Brownwood TX
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Old 06-12-2017, 07:10 PM
Boyd Birchler Boyd Birchler is offline
Join Date: Sep 2014
Location: IN
Posts: 161

Sniffle valve seals off so it does not permit air to be sucked into the intake manifold through the little valve when the engine is running and is open to drain the intake of residual fuel (usually from injector leak down) and oil leaked past the intake valve guides when the engine is not running. If the sniffle
valve is eliminated there is a small chance of sucking these residual liquids into the cylinders and "hydro locking" the engine (bending or even breaking the rods).

Last edited by Boyd Birchler : 06-12-2017 at 07:13 PM.
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Old 06-12-2017, 07:56 PM
N49ex N49ex is offline
Join Date: Apr 2015
Location: Wheaton, Illinois
Posts: 40

I have a new 390 with about 120 hours on it, and in the beginning, had the same drip issue. It has been decreasing, but still happens a bit. This engine replaced a 360, which went the way of a cracked case, but never leaked at the sniffle valve, so the behavior of the new engine was a bit of a surprise. The fuel component is not just injector leak down, it is also any amount of flooding, and then any amount of oil with it makes a mess.

The way I solved it was to run the sniffle valve hose into a little bottle, made from a spice container, so it doesn't end up on the floor and nose gear leg. It takes forever for any significant amount to accumulate, so you can easily dump it at annual time, or oil changes.

Reinhard Metz
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