Buying an A/C with a Low Time Engine

[NavByte]

A very low time engine (less than 100 hours) overhauled only four years ago, with compressions all at or above 77/80 sounded very good to me. However, when the engine shop opened the engine for inspection (due to prop strike) they discovered one of the cylinders has deep corrosion and needs repair or replacement. This means that if they hadn't tear down the engine for complete inspection we could have missed the corrosion. It is a popular practice that we just open a cylinder and take a look inside for corrosion on camshaft, etc. But there is still a good chance that a corrosion in one of the cylinders that we didn't open is left unnoticed.

Is there any other way to notice corrosion other than opening all the cylinders? Does the engine oil analysis reveal such a thing?

 

[Sac Arrow]

If one cylinder is badly corroded, I would be surprised if the remaining cylinders and internal steel hard parts are not. It's been sitting for a long period of time.

 

[Stewartb]

Cylinders are more prone to corrosion when they're low time because all the honing lines are fresh and there's no varnish build up to protect the metal. Internal components aren't more prone due to low hours. When you pull a cylinder you get a pretty good look inside, especially with a Lycoming since you get a view of the cam.

Boroscopes are what's usually used to inspect a cylinder. Very common. And in most cases a little rust haze is no big deal.

 

[Tom-D]

Cylinders are more prone to corrosion when they're low time because all the honing lines are fresh and there's no varnish build up to protect the metal. Internal components aren't more prone due to low hours. When you pull a cylinder you get a pretty good look inside, especially with a Lycoming since you get a view of the cam.

Boroscopes are what's usually used to inspect a cylinder. Very common. And in most cases a little rust haze is no big deal.

Unless you have a very high quality borescope it is very difficult to determine how deep corrosion pits are.

 

[comanchepilot]

where? someplace near salt water?

 

[MAKG1]

If one cylinder is badly corroded, I would be surprised if the remaining cylinders and internal steel hard parts are not. It's been sitting for a long period of time.

Half the cylinders will have all the valves closed. The other half will have either intake or exhaust (or maybe both) open.

 

[NavByte]

where? someplace near salt water?

It's good that you mentioned "near salt water". Why? I think I learned in school that when water evaporates, salt doesn't evaporate with it. So the salt isn't in the air. It's just the moisture.
Any comments?

 

[Fearless Tower]

It's good that you mentioned "near salt water". Why? I think I learned in school that when water evaporates, salt doesn't evaporate with it. So the salt isn't in the air. It's just the moisture.
Any comments?

Personally, I believe general humidity is far more of a factor than 'near salt water'. I have flown a fair amount in California and the East coast. I never saw the kind of corrosion on airplanes in San Diego that I have here living near the Chesapeake Bay.

I have seen far more corrosion on airplanes kept full time in hangars here than airplanes left tied down outside in San Diego. Same distance from the ocean.

 

[tmyers]

How long after the rebuild was the prop strike inspection and how long ago was the prop strike inspection? was the cylinder replaced? did they look at the other cylinders after finding the one with corrosion?

 

[Stewartb]

If the motor in question had a prop strike inspection the mechanic got a close-up of everything and SHOULD have seen any corrosion.

 

[NavByte]

How long after the rebuild was the prop strike inspection and how long ago was the prop strike inspection? was the cylinder replaced? did they look at the other cylinders after finding the one with corrosion?

The prop strike happened last month (about 4 years after O/H) and they are working on the engine now. I'm sure they have inspected all the cylinders and discovered the problem on just this one.
The engine shop said they can remove a little bit off the inside of the cylinder but they have to do it to the opposite cylinder too. This means the two cylinders are going to be a little bigger than the others. So I asked them to just replace the corroded one with a new cylinder.

 

[airdale]

... I think I learned in school that when water evaporates, salt doesn't evaporate with it. ...

Yup. That used to puzzle me, too. I think the answer is that when spray (from wave crests, for example, or waves hitting a breakwater) evaporates in the air, the salt in it becomes tiny airborne particles.

 

[Fearless Tower]

Yup. That used to puzzle me, too. I think the answer is that when spray (from wave crests, for example, or waves hitting a breakwater) evaporates in the air, the salt in it becomes tiny airborne particles.

You see that on metal objects located very close to water (few hundred yards, not a few miles).

 

[Jeff Oslick]

I have seen far more corrosion on airplanes kept full time in hangars here than airplanes left tied down outside in San Diego. Same distance from the ocean.

I saw one that had been tied down at Carlsbad for a long time that was a complete rust (corrosion) bucket. If you go inland a few miles (Montgomery) it isn't nearly the same issue.

 

[Fearless Tower]

I saw one that had been tied down at Carlsbad for a long time that was a complete rust (corrosion) bucket. If you go inland a few miles (Montgomery) it isn't nearly the same issue.

Probably because it was sitting for a long period of time and yes, Carlsbad is very close to the ocean.

Montgomery is within 10 miles of the ocean, but you don't see that kind of corrosion there.

 

[frfly172]

Low time engines are not always a good buy,depends how many hours it has flown,since overhaul. Also how it was stored if inactive for long periods of time.