Implications of an engine not properly laid up

[Fearless Tower]

Lifting a concept from another thread.....what are the implications of an engine that was not laid up/pickled properly and sat for an extended period of time (say a year or two) with occasional ground runs?

Most of us seem to be in agreement that it is less than ideal, but if you were considering an aircraft with such an engine, would you make an offer based on immediately pulling the engine and having it overhauled or would you make a discounted offer with the expectation that the engine probably won't make it to TBO?

IOW, would you be concerned that the result of improper lay up would lead to catostrophic engine failure or just reduced engine life?

Discuss....

 

[Dan Thomas]

Those "occasional ground runs" do far more damage than just letting it sit. Combustion gases get past the rings and since they contain water, a mix of water and oil results and forms acids in the crankcase that eat the engine alive. If an engine flies it will get hot enough long enough to boil that moisture off.

Dan

 

[Bob Noel]

I own a cherokee 140 and I'm have not been able to properly use it the past few years (caring for elderly parents, etc).

For the purpose of pricing it for sale, I take the lack of use into account. Basically, I'm pricing it as having a runout engine.

I know the conventional wisdom is to get an airplane equipped the way you want it instead of doing the mods yourself. However, having bought a supposedly well-equipped airplane with low time engine SMOH and been burned by the need to overhaul the engine well short of TBO (not to mention being bitten by the upgrade bug), I would much rather buy a runout and do the repairs/upgrades myself.

Besides, I like working on airplanes even though I can only do owner-assisted.

 

[Skylane81E]

If PROPPER inspections are done the engine won't make TBO. The cylinder walls, cam shaft, and every other steel part in the thing rust.

If you don't catch it before it progresses to far then you could have a quiet engine when you weren't expecting it.

 

[Jim Logajan]

Those "occasional ground runs" do far more damage than just letting it sit. Combustion gases get past the rings and since they contain water, a mix of water and oil results and forms acids in the crankcase that eat the engine alive. If an engine flies it will get hot enough long enough to boil that moisture off.

Sorry for being stupid about this - but what if the engine is run a long time on the ground? Would that make any difference?

I ask because on the one hand I read posts and articles saying that idling an engine while waiting a long time on the ground before taking off can cause engine overheating, and now on the other hand I read about running on the ground not getting the engine hot enough to boil moisture off.

And on the third hand I've seen the same people write that flying an engine often is good for it.

I think I've run out of hands.

Pointers to some outside credible sources would be a nice start.

 

[Skylane81E]

Oil temps vs. hot spots on the cylinders...

 

[Skip Miller]

Sorry for being stupid about this - but what if the engine is run a long time on the ground? Would that make any difference?

I ask because on the one hand I read posts and articles saying that idling an engine while waiting a long time on the ground before taking off can cause engine overheating, and now on the other hand I read about running on the ground not getting the engine hot enough to boil moisture off.

And on the third hand I've seen the same people write that flying an engine often is good for it.

I think I've run out of hands.

Pointers to some outside credible sources would be a nice start.

Sorry, I have no pointers.

As Dan said albeit briefly, you have two areas of concern: Cylinder temps and oil temps. A ground run, without adequate airflow through the cylinders: you run the choice of overheating the cylinders while trying to get the oil hot enough, or taking it easy on the cylinders and loading the oil up with water.

So fly it or pickle it.

-Skip

 

[poadeleted20]

Sorry for being stupid about this - but what if the engine is run a long time on the ground? Would that make any difference?

No. You need to get the oil temp up above 160-170F and keep it there for at least 30 minutes to cook out the moisture in the oil. You won't do that on the ground without the CHT's going out of sight, and that will cause other serious problems. And that is straight out of Lycoming's Key Reprints and other service publications.

 

[Jim Logajan]

Sorry, I have no pointers.

I found this Lycoming service letter, which is authoritative enough for me:

http://www.lycoming.com/support/publications/service-letters/pdfs/SL180B.pdf

EDIT: And here is the Teledyne Continental letter:
http://www.tcmlink.com/pdf2/SIL99-1.pdf

 

[poadeleted21]

What about an engine sitting in a hangar in death valley?

 

[BillTIZ]

What about an engine sitting in a hangar in death valley?

Sitting and never run? It will survive better than one that is occasionally run on the ground and never flown. Even in death valley, the act of combustion in the cylinders will push moisture and other acids into the engine crankcase and contaminate the oil.

 

[Geico266]

No. You need to get the oil temp up above 160-170F and keep it there for at least 30 minutes to cook out the moisture in the oil. You won't do that on the ground without the CHT's going out of sight, and that will cause other serious problems. And that is straight out of Lycoming's Key Reprints and other service publications.

Rotax want the 912 / 914 engines to get to 200f at least once a flight day.

Burning 1 gallon of fuel produces 1.2 gallons of water. Certainly, some of this water vapor makes it's way past he rings and into the oil. Getting the temps to 200f - 230f once a flight is a good thing in any engine.

Removing the oil dip stick after landing confirms the release of water vapor in my IO 540.

 

[Tom-D]

Must I say it again,?

Every engine is a Pandora's box, You never know what you have.

some engines will set for years and nothing happens to them. others will rust after being pickled properly.

Some engines will not have enough blow by to carry the water out of the breather pipe no matter how long or hot you run them. Other will look like a steam engine in 5 minutes.

Making service bulletins that amount to a lawyer driven CYA requirements do not fit all engines or all conditions that we run our engine.

Any water that is in the engine when you shut it down will stay there, it will condense out to the walls and parts inside of the engine, and these walls are oily, so the droplets drain down into the sump and sink under the oil, (water is heavier than oil) so it basically isolates its self from the engine. (except the bottom of the sump)

There are only two things you as an owner operator can really do to slow down the internal corrosion in any engine.
One is to remove the oil filler cap while the engine is hot and allow as much water vapors to escape as you can. That will lessen the amount of water that stays in your engine.

The second is use an oil that has corrosion inhibitors formulated in. EXXON ELETE is the best of that bunch, In My Humble Opinion.

There are no hard and fast rules to prevent corrosion in the engine, running long periods and raising the temps only produces more water to deal with. It all amounts to how much water was left in the engine when you shut it down.

 

[Skylane81E]

Rotax want the 912 / 914 engines to get to 200f at least once a flight day.

Burning 1 gallon of fuel produces 1.2 gallons of water. Certainly, some of this water vapor makes it's way past he rings and into the oil. Getting the temps to 200f - 230f once a flight is a good thing in any engine.

Removing the oil dip stick after landing confirms the release of water vapor in my IO 540.

Not pulling the filler cap on a conti 360 can cause major rust as the inside of the filler neck rusts away.

 

[Sac Arrow]

No. You need to get the oil temp up above 160-170F and keep it there for at least 30 minutes to cook out the moisture in the oil. You won't do that on the ground without the CHT's going out of sight, and that will cause other serious problems. And that is straight out of Lycoming's Key Reprints and other service publications.

That's true with almost any engine.

 

[Tom-D]

That's true with almost any engine.

There are a lot of dry sump engines that will have no effect what so ever.

The oil is stored in the oil tank and will never get hot enough to boil water. Water boils at 212 degrees F, would you like your oil to get that hot?

Use common sense and think about it, the theory doesn't even make sense.

 

[Sac Arrow]

There are a lot of dry sump engines that will have no effect what so ever.

The oil is stored in the oil tank and will never get hot enough to boil water. Water boils at 212 degrees F, would you like your oil to get that hot?

Use common sense and think about it, the theory doesn't even make sense.

Okay, you got me. I classify dry sump engines in the "almost" category. Yes I agree with that.

 

[Tom-D]

Sitting and never run? It will survive better than one that is occasionally run on the ground and never flown. Even in death valley, the act of combustion in the cylinders will push moisture and other acids into the engine crankcase and contaminate the oil.

here is an engine that had 32.4 hours on it Total time since new, before it ate a bunch of willows was removed from the wreck pickled and sat for 2 years before I tore it down and took these pictures.

tell me how much the pickling did to help?

What is missing in these pictures?

 

[Tom-D]

Not pulling the filler cap on a conti 360 can cause major rust as the inside of the filler neck rusts away.

That same theory applies to Lycoming Cams, they are in the top of the engine and that is where the water will condense first, stay the longest and do the most damage.

dumb place to put a cam.

 

[BillTIZ]

here is an engine that had 32.4 hours on it Total time since new, before it ate a bunch of willows was removed from the wreck pickled and sat for 2 years before I tore it down and took these pictures.

tell me how much the pickling did to help?

What is missing in these pictures?

I didn't say it would survive, I said it would survive better. People think just because they think "Death Valley" that means no moisture.

If it was properly pickled, I see zero oil film.

 

[Tom-D]

If it was properly pickled, I see zero oil film.

It's difficult to take pictures with the oil in the engine

study this picture and tell me what are the two finishes you see on the parts.

this is not a trick question.

 

[denverpilot]

What about an engine sitting in a hangar in death valley?

Engine might survive but all the rubber and plastic parts and hoses will crack and break off the next time the engine is started.

 

[Capt. Geoffrey Thorpe]

Must I say it again,?

Every engine is a Pandora's box, You never know what you have.

Bingo.

Likely it won't make TBO, but likely it won't grenade next week.

Rust in the bores? If you have pitting, it will use more oil. Potentially lots more. I had a car that had so much blow by you had to keep the windows open at a stop light so you could see out (broken rings) I also acquired an outboard motor that had rusted enough to seize up. A big wrench on the flywheel broke it loose. Continued to use it for years.

Camshaft? You can wipe a lobe(s) and loose power to one (or more) cylinder(s). Or lose a mechanical fuel pump (Had a car that did that too.)

Main / Rod bearings? They tend to get noisy - that's a good sign that they need to be replaced. (Seen that too)

It's possible for a rod bearing to seize up and make a new hole in the case. But that ususally happens when you run out of oil.

Swallowing a valve can happen, but is that likely to be caused by corrosion?

What else?

 

[Fearless Tower]

Bingo.

Likely it won't make TBO, but likely it won't grenade next week.

Rust in the bores? If you have pitting, it will use more oil. Potentially lots more. I had a car that had so much blow by you had to keep the windows open at a stop light so you could see out (broken rings) I also acquired an outboard motor that had rusted enough to seize up. A big wrench on the flywheel broke it loose. Continued to use it for years.

Camshaft? You can wipe a lobe(s) and loose power to one (or more) cylinder(s). Or lose a mechanical fuel pump (Had a car that did that too.)

Main / Rod bearings? They tend to get noisy - that's a good sign that they need to be replaced. (Seen that too)

It's possible for a rod bearing to seize up and make a new hole in the case. But that ususally happens when you run out of oil.

Swallowing a valve can happen, but is that likely to be caused by corrosion?

What else?

Thanks, this is what I was basically looking for. So, you basically have a 'low time engine' that isn't really low time at all and could be expensive to maintain/deal with, but doesn't necessarily need to be replaced (assuming nothing horendous is identified on the pre-buy) before you fly the airplane away. Is that what I am hearing?

 

[Capt. Geoffrey Thorpe]

Thanks, this is what I was basically looking for. So, you basically have a 'low time engine' that isn't really low time at all and could be expensive to maintain/deal with, but doesn't necessarily need to be replaced (assuming nothing horendous is identified on the pre-buy) before you fly the airplane away. Is that what I am hearing?

Works for me. :wink2:

I would want to know that someone has flown it a couple hours recently. And I wouldn't pay a "Fresh overhaul" kind of price.
But, well, you don't know how it will run until you run it for a while.

No shortage of 5-10 hours per year aircraft out there flying right now.

(Of course, I ain't no A&P, as I assume you know.)

 

[pmanton]

I have 2 Continental C-85 engines in my hands. 1 was outside in the Pacific Northwest for 12 years. The engine was run a few times, the prop turned a few times, the plane was never flown.

Cylinders were pitted, cam was pitted, several lifters were pitted, the crank was junk, all gears were fine.

The second engine was about 150 feet away but in an open hangar under cover. It was never run, the prop was never turned. So far the engine looks fine, bore scope looks good. I intend to run it as is and see what it looks like after a couple of hours or so.

Paul
N1431A
N83803
2AZ1

 

[Dan Thomas]

There are a lot of dry sump engines that will have no effect what so ever.

The oil is stored in the oil tank and will never get hot enough to boil water. Water boils at 212 degrees F, would you like your oil to get that hot?

Use common sense and think about it, the theory doesn't even make sense.

Water has a vapor pressure, like any other liquid. The warmer it gets, the higher the vapor pressure, and if that pressure is released, the water will evaporate faster.

So water does not have to "boil off." It just needs to get warmer so that it will evaporate in the case and get pushed out with the blowby gases, and get pushed out faster than new moisture is being introduced. A hot engine, moreover, has tighter clearances and will have less blowby than when cold and the crankcase will dry out.

Water evaporates off the ocean and travels inland so we get rain. The tropics get more rain because the ocean is warmer. The ocean did not boil.

From http://en.wikipedia.org/wiki/Evaporation

Quote:

"Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures."

The TCDS for various engines lists the maximum oil inlet temperatures. Typically, we see limits of 225 to 245 °F. That's the oil inlet, after it has passed through the oil cooler. The oil leaving the engine will be considerably hotter than that, possibly 275° or more.

Dan

 

[Tom-D]

Water has a vapor pressure, like any other liquid. The warmer it gets, the higher the vapor pressure, and if that pressure is released, the water will evaporate faster.

So water does not have to "boil off." It just needs to get warmer so that it will evaporate in the case and get pushed out with the blowby gases, and get pushed out faster than new moisture is being introduced. A hot engine, moreover, has tighter clearances and will have less blowby than when cold and the crankcase will dry out.

Water evaporates off the ocean and travels inland so we get rain. The tropics get more rain because the ocean is warmer. The ocean did not boil.

From http://en.wikipedia.org/wiki/Evaporation

Quote:

"Since the kinetic energy of a molecule is proportional to its temperature, evaporation proceeds more quickly at higher temperatures."

The TCDS for various engines lists the maximum oil inlet temperatures. Typically, we see limits of 225 to 245 °F. That's the oil inlet, after it has passed through the oil cooler. The oil leaving the engine will be considerably hotter than that, possibly 275° or more.

Dan

Then why do we need to run 30 minutes?
if evaporation is the method, why not leave the oil filler cap off, and allow evaporation to take care of the problem?

 

[Fearless Tower]

Then why do we need to run 30 minutes?
if evaporation is the method, why not leave the oil filler cap off, and allow evaporation to take care of the problem?

How is the water going to evaporate with the cap off when it is at the bottom of the sump under the oil?

 

[Tom-D]

How is the water going to evaporate with the cap off when it is at the bottom of the sump under the oil?

That is a problem isn't it.

and what will bring it off the bottom of the oil sump?

it certainly won't get stirred that much and heat won't do it either. do you believe the oil pump will move enough oil to bring it out?

oil sump and crank case of a Lycoming 0-360

 

[Dan Thomas]

That is a problem isn't it.

and what will bring it off the bottom of the oil sump?

it certainly won't get stirred that much and heat won't do it either. do you believe the oil pump will move enough oil to bring it out?

The oil pickup is at the bottom of the case in any engine I've had apart, and the turbulence and vibration would in any case shake it around plenty. It takes time to evaporate that water, and the colder the case and oil, the longer it will take.

If the water did not evaporate during the run, it would continue to accumulate until it filled the crankcase.

Dan

 

[Tom-D]

The oil pickup is at the bottom of the case in any engine I've had apart, and the turbulence and vibration would in any case shake it around plenty. It takes time to evaporate that water, and the colder the case and oil, the longer it will take.

If the water did not evaporate during the run, it would continue to accumulate until it filled the crankcase.

Dan

oil pump pick up tubes are never all the way at the bottom of the sump, or they would pick up the sludge and debris that settles out.

Lycoming's suction screen is about 1/4" off the bottom. (see the pictures) suction screen and drain plug right next to each other.


So how does it get out? .... by the drain plug at oil change.