The Cessna 120-140 Association Forum

Looking to purchase a 120 that was overhauled in 2010. Then it sat from 2014-2021 though notes in the logbook state it was started 3-4 times per year.

I’m not worried about the sitting since it’s been flying since then and seems to have been well taken care of. My big concern are the cermicrome cylinders. I’ve read how they can start to fail with pretty low hours. I’m not sure how widespread that was but this plane has 306 SMOH. Last three years of annual compression checks are below. Any thoughts from anyone that has experience with these?

2021: 78/76/78/75
2022: 72/74/78/78
2023: 70/72/74/72

We have ECI cermicrome cyl. on our C-90 installed about 2010 450 smoh and no problems and great compression running Aero Shell 100plus after mineral brake in. Not sure why those compression's are declining maybe needs some Marvel Mystery oil to clean things up and some good hard run time?

Thanks, Jeff! Knowing less than a little bit like I do, reading a couple of bad things on the Internet gets you worried. Glad to hear some positive comments to balance that out.

I'm not sure I'd lend too much credence to the apparent decline in compression readings. It could just as easily be a decline in the accuracy of the tester. Do you know how many hours have been put on it in the last 3 years?

I agree, could be a number of things. Just trying to do my homework!

It’s had about 80 hours put on it since 2021.

Superpilotjustin,
I'd be much more worried about crank/cam corrosion than cylinder compressions. All those ground runs over the years are about the worst thing they could have done for that engine. The engine won't get hot enough to burn off the water that is being added each time it was run. That water sits on steel parts like the crank and cam and start rusting.

Just because it ran fine the last 80hrs doesn't mean the engine is good to go. Cam wear from corrosion won't always show up immediately. It could take 50hrs, 100hrs or so. Then you start getting metal in the filter/screen and it's all over but breaking out the checkbook for the overhaul. Overhauls at good shops START at $30K nowadays and go up from there if you need a crank, cam or crankcase.

If you do move forward make sure the oil has some time on it, like 10 or 15hrs and have a mechanic pull the oil screen and inspect very closely. The metal also shows up in the bottom of the housing below the screen (just in front of the threads) and this area should be inspected close. I begin by swiping the oil puddle with a magnet. Then wipe the puddle of oil with a clean paper towel and if there is any metal you will see it on the paper towel and the magnet. Be wary if the oil has been changed immediately before you inspect the screen...the owner could be hiding the fact that he found metal at the last oil change and hoping none collects for your inspection. If it has an oil filter, the mechanic will cut open the filter and inspect the pleats for metal. Even with all of this, I think it's a gamble on whether or not that engine is going to need an overhaul soon or serve you faithfully for a long time.

I tell people who ask how long our engine last that they rust out before they wear out unless you fly them regularly.
Josh

Thanks, Josh. I appreciate the good info. I’ve had a hard time locating someone to look at the plane for me, but will relay this once I (hopefully) find someone.

No problem Justin...I hope my post didn't come off as gloom and doom. My intent is to give you as much information as possible.

To expand on the "gamble" comment above...any plane purchase is a gamble. Even a perfectly maintained and often flown engine can have problems. I'm overhauling my engine right now as it decided to crack the crankcase 1200hrs after the last OH. My point is an engine that has sat for 7yrs and been ground run instead of flown is "more" of a gamble than one that was flown regularly.
Josh

Not at all, the perspective is much appreciated!
First time buyer so I need all the info I can get.

You can have them run it up one more time and take an oil sample. Have it analyzed and have the screen or filter inspected. Or, pull a cylinder off and get eye on the cam lobes themselves.

I think the cermichrome cylinder bores are supposed to resist rust, so that's one thing in your favor.