Best way to Check on Engine that has been Sitting

Dennis M Carleton

Dennis M Carleton

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What should be done before flying an engine that has flown only 20 hours in the past 7 years? Is the major concern here corrosion on the crankshaft and cam shaft? Are there any indicators, short of pulling a cylinder and doing a visual inspection? Cylinder compressions are all in the 70s.

Thx!
 
Buy it and hope? I've never heard of a seller allowing a prospective buyer to tear into an engine for a look.

You could make a bid deal out of it and price an overhaul into the airplane price. The seller won't like it, so you'll go find a good example of the type you want to buy.
 
Take a step back and consider "What should be done before starting or even turning over an engine that has been run only 20 hours in the past 7 years"
There are many useful and preventative things that can help an engine to better come out of a long coma. Im not an A&P to say but doing a compression check on such an engine wouldn't be my first step.
 
Borescope everything. The total time is important too. If you have a lot of varnish on the parts that's one thing as far as protection. If they were clean before the lack of use, that's another. Remember the mags too.
 
11 of the hours were flown since July. Compressions were from July as well.
 
The seller is going to think that the engine is worth what a new engine is. To you, it's X% chance or Y hours away from being worth what a core is. There are a lot of optimistic people out there, that see rainbows and unicorns all the time, and they believe X is close to zero and Y is close to recommended overhaul time. So you'll have to decide if you want to pay X thousand dollars more for a plane than it's worth to get this one. I see this as a math or negotiation problem more than a mechanical problem.

If you want to negotiate, you might start with trying to come with a number between you of how many hours you think the engine has left. I'd probably try to land on maybe 500, and that's still sounds like a big risk to me. 0 is safe. 2000, nuts, in my view. But all the plane prices are crazy high now, so who knows. People seem to be dragging planes out of old barns to sell.
 
Bell206 said:
Is the aircraft still in annual? Flyable?
What does the rest of the aircraft look like?
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Plane is in annual and flying. Rest of the plane is beautiful. Updated interior, redone panel, new AP, etc. Engine has about 700 hrs SFRM.
 
Dennis M Carleton said:
11 of the hours were flown since July. Compressions were from July as well.
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Dennis M Carleton said:
Plane is in annual and flying. Rest of the plane is beautiful. Updated interior, redone panel, new AP, etc. Engine has about 700 hrs SFRM.
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Thank you Paul Harvey, for the rest of the story. :) (damn, does that date me? I listened to him while riding my Dads lap:))
That changes the entire outlook to me. I was going with the assumption that it was overhauled and then parked shortly afterwards. I'll now bet that its been hangared as well. The longer an engine runs it gets a film/varnish from all the oil mist and heat, on non-friction surfaces, that bakes on and acts like a rust inhibitor. Any damage that may have happened was done in that first hour back in July.

I'll second @Bell206 A beautiful plane you like with a price you're happy with, a 700hr engine that might need work no matter if it sat for decades or flew everyday? Buy it while you can.
All buyers are optimists, should any pessimist be a pilot?
 
If it ends up using a lot of oil, what’s it cost to pull the engine and replace the crankshaft?
 
If it end up using a lot of oil, the problem is not the crankshaft.
 
Dennis M Carleton said:
What should be done before flying an engine that has flown only 20 hours in the past 7 years? Is the major concern here corrosion on the crankshaft and cam shaft?
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Yeah, those would be the main concerns, but the condition may vary based on where it’s been sitting. Honestly, I’d refresh the accessories if they haven’t already been and fly the dog snot out of it!
 
Lycoming recommends the engine be overhauled every 12 years regardless of total time. If the engine is 12 years old I would just factor in a full overhaul into the price. Then I would fly it for a while and hope!
 
I don’t see the type of engine? No location either, could matter. How about the years since this engine was new? Another factor.

The way things are now, could easily be sold in a matter of days. Someone will be willing to give it a go.
 
My thought would be to pull the Left mag.

It lives in the same “house” as the cam and cylinders so it can provide an

indication of the rust factor.

The other reason is to replace the Impulse Coupling Spring.

Springs are not tolerant of any rust and tend to fail if any is present.
 
Robert Gee said:
If it end up using a lot of oil, the problem is not the crankshaft.
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It sure can be the crankshaft. The cylinders are lubricated by oil thrown off the crankshaft, and that oil came from between the crank's rod journals and the rod bearings. There are clearances specified for the small gap between the journals and the bearings, and if those clearances get larger, more oil is flung into the cylinders and the oil control rings eventually can't gather it all and pull it back into the crankcase. All the rings begin to "hydroplane" on all that oil, letting it get past the rings and into the combustion chamber, where it gets burned and exhausted (and forms lots of carbon on everything).

An engine suffering from internal corrosion can get crankshaft journal pitting, and so can the bearing shells. Pitted journals wear away at the bearing shells, too. More oil gets past, more oil is burned. A bad sign is falling oil pressure as the clearances get so big that the oil pump can't keep up.
 
Compressions don't necessarily mean squat. Cylinders that are pumping oil frequently have good compressions. If this is a Lycoming, it would be prudent to pull a cylinder and get a peek at the cam and lifters. The cylinders can be easily borescoped. What you find is the basis for price negotiation. Depending on the environmental storage conditions, the engine might run happily and safely for a while, or could be on the path to self-ruination in a short time. Another thing to know is how much oil this engine is using since it has started flying again. Even with an internal inspection, there are no guarantees. With any engine you didn't overhaul yourself, you should be prepared to bite the bullet to refurb and engine at any time. I personally wouldn't pay full value for any engine that was not flying regularly, regardless of what it looks like during a limited inspection.
 
chemgeek said:
Compressions don't necessarily mean squat. Cylinders that are pumping oil frequently have good compressions. If this is a Lycoming, it would be prudent to pull a cylinder and get a peek at the cam and lifters. The cylinders can be easily borescoped. What you find is the basis for price negotiation. Depending on the environmental storage conditions, the engine might run happily and safely for a while, or could be on the path to self-ruination in a short time. Another thing to know is how much oil this engine is using since it has started flying again. Even with an internal inspection, there are no guarantees. With any engine you didn't overhaul yourself, you should be prepared to bite the bullet to refurb and engine at any time. I personally wouldn't pay full value for any engine that was not flying regularly, regardless of what it looks like during a limited inspection.
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An easier thing: take one of the mags off and see if its gear or drive is rusty. Look into the mag's drive pad hole at the other gearing in the accessory case. Moisture in an engine doesn't just attack the camshaft. It goes after everything. A look into a cylinder through a sparkplug hole, using a cheap snake camera, is also informative. Pitting or brown staining of the cylinder wall is not good.
 
chemgeek said:
Compressions don't necessarily mean squat. Cylinders that are pumping oil frequently have good compressions. ...
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Not sure I'd go that far, but ...
Back in the far, distant past, when people did stuff like this, before vehicles became "devices", it was not unknown to squirt a bit of 30 weight into each cylinder of a well-used car, so when a prospective buyer came by and checked the compression, it would seem good.
 
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