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Oil out of sniffle valve

B

Bavafa

Well Known Member
I have now just over 70 hours on my IO-360-M1B and after every flight I get about a cap full of oil out of my sniffle valve. This has been since day one and I had been hoping for it to go away but it persist with roughly the same amount after each flight. The engine was brand new. Just wondering if any one has any thoughts/experience as this?

Thanks in Advance
N825SM - RV-7A
Mehrdad
 
It?s actually fuel oil mix, the fuel evaporates and leaves the oil then the oil drips out the bottom of the cowl, this is normal and is what the valve is there for and yes mine does it to. I just wipe off the forward belly every couple of flights.
 
My XPIO360 does the same thing,

I added a short piece of 3/8" soft aluminum tubing bent to move the mess just aft of the cowl outlet. Used rubber fuel line to connect to the sniffle valve, and bent the outlet down to keep fuel and oil off the exhaust pipes. Now the mess is only on the floor.

I'd like to remove the sniffle valve to get rid of the mess, and a little extra top end oil might not be bad on startup (thought carbon deposits from the oil might be a negative). However I do like the way the valve drains any extra fuel from the intake manifold on a hot start (if I get too heavy with the boost pump), and if water ever gets past the intake filter and the weep hole in the FAB, the sniffle valve is there to protect the engine from the water.
 
I have the same aluminum tube

that directs the oil/fuel to the outside of the cowl and the mess is only on the floor. But my point/concern is that how does oil gets to the intake sump? Only fuel is suppose to come out of this and not oil.
One logical explanation is that it getting pass the intake valve guide but I am wondering if that is normal?

Regards
Mehrdad
 
I removed the valve and put a plug in the hole. To start my engine hot, I leave the mixture control full lean until the engine fires then I slowly richen. Works great and no mess in the cowl or on the floor. To crank the engine cold, I run the boost pump for 2 to 3 seconds with the mixture full rich then crank the engine. It has never failed to start. It seems that injected engines require more cranking than carbureted engines though.

David Watson
RV8 in process and Starduster flying.
 
Bavafa said:
that directs the oil/fuel to the outside of the cowl and the mess is only on the floor. But my point/concern is that how does oil gets to the intake sump? Only fuel is suppose to come out of this and not oil.
One logical explanation is that it getting pass the intake valve guide but I am wondering if that is normal?

Regards
Mehrdad
Click to expand...

There is fuel there to but the fuel evaporates very quickly leaving just the oil behind. Is oil in the induction normal? I would say yes, the barriers that keep oil out of the ?top? are not 100% so oil does get buy both the rings and the valve guides/seals even in the healthiest Lycoming. What you have going is normal.

I do think that shutting the fuel off and running the engine out of fuel helps create a little less mess. I think that if you shut down with the mixture and come back the next day and see that the fuel pressure is 0 then I assume the fuel pressure leaked out to the cylinders running into the induction and possibly the cylinder boars. Not 100% sure about this though.
 
Thanks for the feedback. A number of folks have confirmed that it normal to get a bit of oil out of sniffle valve, but then again a few others/mechanics say? it is not.

Then engine seems very healthy with no issues and I always shut it down with the mixture control.

Regards
Mehrdad
 
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