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Old 03-16-2017, 06:51 PM
Aussieflyer Aussieflyer is offline
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 49
Default Running In the Lycoming YIO 390

Thought I'd share my experience with running in my new YIO-390. I read the Lycoming material carefully. I used no power settings less than 82% power. Thanks to Van's design for the baffles, never had a temperature problem. At 40 hours the oil consumption appeared to have stabilised at around 1 quart for 22 hours operation. I changed the mineral oil out and used Shell 100W plus. Did a leak down test and got four 80/80's rings and valves nice and tight. Within two hours operation on ashless dispersant oil I started getting a puddle of oil on the floor after every flight. Examination revealed the oil was dripping out of the sniffle valve (intake manifold one way valve). I asked Lycoming what they thought and got no response (not impressed with their customer service).

A local Lycoming mechanic told me that I'd taken the run in oil out too early, he said the IO-390 should be run in up to 100 hours. I was instructed to take out the 100W plus and immediately replace it with run in oil (mineral oil) and to go and fly the aircraft for the next 50 hours at wide open throttle (WOT) not above 5000 feet (the lower the better). After the first 2 hour flight - bingo no more oil coming out of the sniffle valve and not a drop since.

I just finished reading a nice article in April's 2017 Kitplane magazine by Reinhard Metz on the IO-390, where at page 46 where he writes, "One thing that is not so well known about the IO-390: The typical approach to break-in is to run the engine hard in first flight(s) (and with power variations) to press the rings out and help them seat...... The IO-390 doesn't behave this way. According to Lycoming, and true to my experience, the IO-390 rings may take as long as 50 hours or more to seat and for the oil consumption to drop. Apparently they are made of harder material, which is responsible for the longer break-in and supposedly have a longer service life. Hmm, well see."

Hope this thread is useful for those following. Anyone got similar experiences?

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Old 03-16-2017, 08:01 PM
frghtdg frghtdg is offline
Join Date: Feb 2016
Location: Boynton Beach, Florida
Posts: 62

Keep adding updates as you add hours as many of us are about to start the process.
Good information.
N14HN Phase 1
Sailplane Racing
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Old 03-17-2017, 10:56 AM
rvbuilder2002 rvbuilder2002 is offline
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,558

Originally Posted by Aussieflyer View Post
Within two hours operation on ashless dispersant oil I started getting a puddle of oil on the floor after every flight. Examination revealed the oil was dripping out of the sniffle valve (intake manifold one way valve).
It is actually fuel residue.

It is unlikely what you are seeing is oil (though I admit it certainly looks like it). Check it with a white towel/Kleenex and you will likely find that it has a definit dark blue color from highly concentrated fuel dye.

There is no path for oil between the main engine sump and the induction manifold other than the intake valve guides, so accumulation of oil that would drain from the sniffle valve would have to come though the intake valve guides and then migrate down the induction tubes, or have a pathway that shouldn't exist because of a faulty engine casting.

A simple test to prove it, is to run the engine at about 1200 RPM for a minute after a flight and then shut the engine down by positioning the fuel selector to OFF and let the engine quit. This will bleed down all system pressure before shut down instead of it bleeding down into the induction system afterward.

This has been some what common on 390's vs some of the other models for reasons that no one has been able to explain to me.

Point is, it probably has nothing to do with your break in or change of oil type......
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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Old 03-17-2017, 09:19 PM
Jake14 Jake14 is offline
Join Date: May 2014
Location: Seattle
Posts: 167

Not sure if this is pertinent to the post, but after uncrating the engine, when I first looked into the IO-390 intake manifold through the fuel servo opening there was a pool of oil about 6" dia. Since then, because I had to turn the prop, I've squirted about a pint of preservative oil into the cylinders via the top and bottom plugs. Checking the intake manifold now, there is a large quantity of oil..see pic.. apparently the preservative oil I sprayed in. I haven't installed the sniffle valve yet.

Seems like the only way this oil could have gotten into the intake manifold from the cylinders is via the intake valve and intake ports. I haven't run the engine yet...

I asked Lycoming support about this and they said:

"This appears to be residual preservative oil, and should be cleaned out prior to running the engine. I do not suspect that the source of this oil is from a leak or defect"

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Old 03-18-2017, 02:54 AM
rv8ch rv8ch is offline
Join Date: Feb 2005
Location: LSGG
Posts: 2,266

If an intake valve is open, and you put a lot of oil in that cylinder then that oil could flow down to the intake manifold.
Mickey Coggins
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Old 03-18-2017, 05:00 AM
Ron B. Ron B. is offline
Join Date: Nov 2007
Location: Yarmouth, Nova Scotia
Posts: 2,202

I assumed Lycoming put it in thee for long time storage.
Thanks Ron
RV-14 Flying
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