C172 Storage

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1 day 9 hours ago #3465 by STEVE ELLS
Replied by STEVE ELLS on topic C172 Storage
Hi John,
I mistakenly gave you the oil pressures for a Continental engine; the correct operating range (hot cruise power) is 60-90 psi.
The pressure may go above 90 during a cold morning start; it nothing to worry about.
The hot idling oil pressure low limit is 25 psi. If your OP is below 25 at hot idle, this indicates wear in the lower end of the engine.

Best,
Steve

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3 days 2 hours ago #3461 by STEVE ELLS
Replied by STEVE ELLS on topic C172 Storage
Hi John,
In order to know exactly what the OP is, your mechanic will need to disconnect the oil pressure tube from the engine and install what we call a "direct reading gauge" that reads the psi in numbers.

The minimum hot idling rpm for your Lycoming oil pressure is 10 psi. Normal operating range is 30 to 60 psi.

I have a four cylinder Lycoming in my Comanche. Full is 8 quarts. I am comfortable running it down to 5 quarts for short flights (1-2 hours) before I add a quart.

For long XC flights (2 hours or more) I start at 6.5 quarts. However I have old cylinders that have been chromed back to standard bore. The advantage of chrome cylinders is they don't wear and they don't rust. But the oil control rings don't seal as well as the standard steel wall cylinders.

The answer is you experiment. You'll find a level where there is not a lot of oil vented out the crankcase vent tube onto the bottom of the airplane, and where the oil temperature is stable.
Too little oil results in higher oil pressures.

A wise man once told me there are two oil levels in airplane engines. Not enough and enough.
Very few owners keep the crankcase levels full since the first quart seems to "blow out" through the crankcase vent tube (wet oily belly).

Yes, change the filter every time you change the oil. I always cut the metal jacket off the filter (there are special tools you can buy to make this easy from companies such as Aircraft Spruce and Specialty (aircraftspruce.com)
After the can is removed, I cut the paper-like filter media off the center stalk. Then I spread it out and inspect it closely with a magnet and a strong light.

This numbers are OK, but seem to be signaling that wear has occurred. But I would never pull a cylinder based on one lowish compression reading. Get your mechanic to stick a borescope in the cylinder (I use the Vividia Ablescope VA-400 from Oasis Scientific- Amazon $249) and inspect the valves for any evidence of burning.

If the valves look OK, then I would continue to run it. But I would probably change the oil to get new clean oil in the engine. Then after 10 hours I would do another compression test. It will probably be better.

Let me know what you find.

STeve

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5 days 2 hours ago #3455 by John Zarpak
Replied by John Zarpak on topic C172 Storage
THANKS for all the info. I wqill download the M-0 soon. I read what you wrote and have the following questions;
1- What is idling oil pressure?
2- My aircraft (C172P) does not have numbers on oil pressure gauge, only a green band, how can I get the numbers?
3- How do I find my "The sweet spot Oil"?
4- Do I change the oil filter every time I change oil?
5- Two of the cylinders are low, 60 and 65. The person who did the annual (last April) said "It is not important, these readings change all the time". How often should I have them checked for pressure?

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1 week 3 days ago #3442 by STEVE ELLS
Replied by STEVE ELLS on topic C172 Storage
John,

It's not unusual for a four cylinder Lycoming engine to exceed the published TBO if it's flown often and serviced regularly.

I'm sending a link to help determine if your engine is worn out.
Enter this in your search engine: www.piperflyer.org/maintenance-technical...-to-do-about-it.html .

The article will provide some guidelines.

Lycoming service bulletin 1191A provides guidance on compression readings.
I will add that bulletin to this post.

Please read it carefully, The important part is where is says if a compression reading is "low" test it again in 10 hours as these reading do vary over the life of an engine.

Let me know what else you need,

Steve

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2 weeks 1 day ago #3428 by John Zarpak
Replied by John Zarpak on topic C172 Storage
WOW, I did not know that, Thanks Stave and Jen.
As for how long my aircraft would be sitting, I don't know. I just got this aircraft in late April, we have good winters in Maryland so it may be sitting for a month or more in winter in open space -No hanger available.

I read the articles Jen sent and I downloaded the Engine Guide. I do need more information, I am new to this and my engine is old, about 1900 hours with low (70) compression on 2 cylinders. The oil did not go lower than 7 after 12 hours of flight. It is C172P 1982, 160HP. Please do sent me more information.

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2 weeks 3 days ago #3426 by Jen D
Replied by Jen D on topic C172 Storage
Here are links to a couple of articles on the subject - one that Steve wrote a few years ago and another from our Engine Resource Guide.

www.cessnaflyer.org/maintenance-tech/ite...ne-preservation.html

bluetoad.com/publication/?m=66557&i=713057&p=76&ver=html5

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