IO360 Low oil pressure on cruise (55psi)

[EricJ]

48 minutes ago, redbaron1982 said:

Is there an actual IO-360-P1A or IO-360-N1A engine or are these just "fake" names to have a generic IO-360 manual? I've just finished printing the N1A, I think I will throw it away and print the P1A that seems to be more complete.

Use the Overhaul Manual Direct Drive Engine, since it does apply to any direct drive Lycoming.   It covers pretty much everything.

[PT20J]

10 hours ago, redbaron1982 said:

Is there an actual IO-360-P1A or IO-360-N1A engine or are these just "fake" names to have a generic IO-360 manual? I've just finished printing the N1A, I think I will throw it away and print the P1A that seems to be more complete.

According to the 1E10 TCDS, the N1A and P1A are actual IO-360 variants. These maintenance manuals might be useful for general information, but if there is no maintenance manual for your engine variant, then the proper documentation is the overhaul manual plus the applicable service documents.

[redbaron1982]

Hey, today we disassembled the oil pressure relief valve to check if there was any debris that would explain the low oil pressure. It was clean.

Something that caught our attention is that there was only one washer. Being the max 9, this seems a bit on the low side. But there are two versions of the non adjustable valve. One that goes up to 9 washers and the other that uses up to 3 washers to increase pressure and up to 3 spacers to decrease it.

My doubt is which version I have. I couldn't find in the overhaul manual or part catalog which are the p/n for each version.

Mine is P/N 76159, picture attached.

Does anyone identify this as one of this two versions?

[A64Pilot]

Add a washer or two and run it up and see. This isn’t rocket science, if pressure doesn’t change, then it’s not valve shimming. A possibility is the valve seat needs staking.

Don’t be afraid of slight in the red pressure at run up RPM on coldish oil.

May be my Ipad but it looks like there is two crush washers, there isn’t is there? An extra washer there removes spring pressure.

Nice safety wiring

[PT20J]

Lycoming has three valves (in order of latest to earliest design): Externally adjustable, Tall tower, and Short tower. The short tower allows max 3 AN960-10 washers and the tall tower allows up to 9. 

Your picture appears to be a tall tower.  You can call Lycoming tech support to confirm the P/N.

[redbaron1982]

Thanks @A64Pilot and @PT20J. After seeing pictures of both tall vs short towers, mine is clearly the tall tower. So being that the case, I've added 2 washers so I went from 1 to 3 (out of a max of 9 washers). I didn´t go flying, I just did a runup and oil pressure was higher now, being briefly at 105PSI during startup, and then during the runup with oil still on the cool side it was around 90PSI.

After the runup, I checked and didn´t see or feel any oil leaking out of the pressure relief valve.

There is only one crush gasket, but it's true that the picture looks "odd" near the gasket.

That was my first ever safety wiring, the A&P said it was ok, so that's enough for me!

[A64Pilot]

Go fly, with the intent of staying in the pattern for at least one lap, but be sure to fly long enough that your oil is fully warmed up and isn’t getting any hotter then you can hopefully declare victory. Like I said don’t worry about a little in the red for a short time, I believe Lycoming has raised the redline recently, but I’m not sure if they really have nor what the new red line is. Someone will come on and say I expect.

To some extent oil pressure is likely to follow both RPM and oil level, the level I admit confuses me as my oil temp is always low, but let the level get to 5 qts and I’m running at 2300 at the bottom third of the green where 6 qts is the top third.

Personal opinion is I like to be in the upper third. On my engine anything above 6 I might as well smear on the belly, because that’s where it’s going, I’m the guy that does not put 8 qts in at oil change, why some do confuses me.

[redbaron1982]

19 minutes ago, A64Pilot said:

Go fly, with the intent of staying in the pattern for at least one lap, but be sure to fly long enough that your oil is fully warmed up and isn’t getting any hotter then you can hopefully declare victory. Like I said don’t worry about a little in the red for a short time, I believe Lycoming has raised the redline recently, but I’m not sure if they really have nor what the new red line is. Someone will come on and say I expect.

To some extent oil pressure is likely to follow both RPM and oil level, the level I admit confuses me as my oil temp is always low, but let the level get to 5 qts and I’m running at 2300 at the bottom third of the green where 6 qts is the top third.

Personal opinion is I like to be in the upper third. On my engine anything above 6 I might as well smear on the belly, because that’s where it’s going, I’m the guy that does not put 8 qts in at oil change, why some do confuses me.

Yes, regarding oil level savvy recommends adding oil only when 5qt or lower and never put more than 6qt. I still don't feel comfortable with that. My main concern is how low it can go before you start having too low oil pressure or too high temp. Let's say I'm at 5.5qt and I'll do a 4hs flight. Maybe I land with 4.5qt. So how much is too low?

[MikeOH]

I believe Lycoming specifies 2 quarts as the minimum sump quantity for the IO-360 series.

So, how much oil do you burn an hour?  For your hypothetical flight, it better be less than 3.5 quarts in 4 hours

[redbaron1982]

5 minutes ago, MikeOH said:

I believe Lycoming specifies 2 quarts as the minimum sump quantity for the IO-360 series.

So, how much oil do you burn an hour?  For your hypothetical flight, it better be less than 3.5 quarts in 4 hours

I'm still trying to get a oil consumption average but in the 16 hours I flew it went from 8qt to 6.5qt with 3 qt added. So ~4hr/qt.

[DCarlton]

My mechanic has always added 8 quarts at the oil change.  I try to operate between 7 and 7.5 quarts.  I’ve never felt like my oil burn was excessive or there was too much oil blowing out on the belly.  Is this “above average” behavior? I’ve felt like I got a really good overhaul.  
 

[A64Pilot]

I don’t honestly know what my oil consumption is, but I do know at least on my engine anything above 6 qts goes away pretty quick.

Aircraft are not like automobiles, they are allowed to use a whole lot of oil and still be airworthy, so therefore logically they have to carry enough oil so that even at maximum oil consumption that they can fly until the fuel tanks are empty before oil level gets too low.

So about the only way you can assure that is to overfill the oil, so “full” on an aircraft is actually arguably over filled.

According to Lycoming we are allowed to use .65 quarts per hour and that’s acceptable (if I didn’t make a math mistake) and a 200 HP engine.

So if you flew for 8 hours, that’s 5 quarts of oil, with an oil consumption like that better not start with 6  if your going on a long flight.

https://www.lycoming.com/sites/default/files/attachments/Lycoming%20Reciprocating%20engine%20Break-In%20and%20Oil%20Consumption.pdf

 

[A64Pilot]

Decent article on the subject

https://generalaviationnews.com/2016/05/02/what-oil-level-is-best/

By the way, it’s been this way for longer than most of us have been alive with no changes

[Gocaps]

On 5/8/2023 at 3:27 PM, PT20J said:

There is no such thing as a Lycoming service manual. Traditionally, Lycoming produced an overhaul manual, an operator's manual, and all additional information was contained in service literature (letters, instructions, bulletins). Many, many years ago, the FAA mandated a requirement to create maintenance manuals that included airworthiness limitations. Because of the shear number of products involved, Lycoming got the FAA to delay the requirement. A few years ago, the FAA finally made Lycoming begin creating maintenance manuals, but they are only available for some later models. The only IO-360 maintenance manual that I'm aware of is for an IO-360-N1A. It's probably very similar to what a maintenance manual for an IO-360-A3B6(D) would be if there was one, but there may be differences. I believe that the overhaul manuals must be purchased, perhaps with a subscription. 

There is no "service manual"  So what are they referencing when they have "Refer to the section “blah blah blah” in
Chapter 74-20 of the IO-360-N1A Engine Service Manual"