Key pre-buy checklist points on engine related items

Since the last thread was so successful, I decided to see if I could find another pot of gold with this thread. Mike, if you have any more article links, I would love to have them.

The plane I am going to pre-buy this week has a relatively high time engine. I realize that the answer to this question varies somewhat with engine type/make/model, but in general terms, what are some of the major checkpoints one should hit when trying to determine the state of the engine, and if it stands a chance of hitting TBO vs falling apart the day after you purchase? I want to be there and to make sure my IA does what I need and want, and while I do trust him as an IA, I don't truly trust anyone, so I want my own list to compare against.

For the sake of argument, lets narrow this topic to typical 100LL burners, typically found on single-engine aircraft. Nothing trubine or exotic.

Do you think if you told us what make and model engine you have it might be helpful?
Some are known to go to tbo, some are known to have trouble.
You can fly look in the log books, and see if it has been awhile since the last oil change. If so, do a warmup flight, then have the a&p pull the filter and check for metal. You may want to do an oil sample and send it for analysis, takes a few days. Don't do it if the oil has just been changed. You can also see if it is burning much oil, look in the exhaust, but you can have a high time engine that burns some oil and the lower end is still good.

It probably would, but I was hoping for more of a general conversation. Things like:
Compression: Cont. 40+ on all cylinders, Lycomings 60+ on all cylinders (I think those are the correct numbers, but what does this really meen in a # of hours remaining vs $ that will need spending?)
Oil screen/filter: No metal fragments found. If some found, X amount is OK (or not)...quantify X
Oil leaks: Many/Most engines seep oil, what locations are OK/expected vs big no-no's
Engine wiring: What are examples of good/bad repairs? Pictures?
Corrosion: What is normal/expected vs bad in the cases that are not obvious? For example, any steel part, like starter rings, will likely have surface corrosion...what is expected vs too much in the "fringe" cases? Are the "acceptable amounts" somewhat dictated by the location in the country (close to the ocean vs inland)?
etc.

Obviously you must trust your A&P to a degree, but pictures are worth 1000 words, and the more informed one is, the better they can question the findings. I realise experience is a key player in all of this, which is why this is a great forum for those more experienced to share what they know. Including pictures of "barely good" vs "not acceptable" would be a great touch!

Hey, Tom's not doing anything these days...maybe he wants to be Administrator.

If I was buying a plane that's close to TBO or any other needed inspection, it's going to be done before the purchase or the deal is going nowhere.

The manufacturer does make a difference. Continentals have different weak points than Lycos. The cylinders have problems in different areas for instance. Continentals vs Lycos have different criteria for what is passing for a compression test. The cases fail in different places, etc.

And then you get into the different cylinder bore treatments - steel, traditional chrome, cermi, etc.

Lots of stuff to consider. No real one size fits all list of stuff to look for.

Regards,

Wes
N78PS

The price of an airplane with a high time engine should reflect that fact for starters, so the risk associated with that condition should be well considered.

With any engine you will want to look at the engine logbook. See what has been done and when, from routine service to major repairs. Engines that don't fly much are very prone to corrosion damage, especially cams and lifters in Lycomings. If the engine was previously overhauled, who did the work? Is there a list of replaced parts available? There is a lot of difference between a good overhaul and a not so good one. Of course, check the compression and oil filter. If you have access to a borescope, it woudl be nice to take a look inside the cylinders, especially any of them that are at all marginal on compression.

It is always good to have someone who is familiar with that model of engine take a look at things. Some engines are prone to cracking in certail places or have other peculiar problems. general advice is not going to be enough help to find those problems. ADs are also an issue. Some of them are pretty expensive, like the Lycoming crankshaft AD that many people failed to deal with when Lycoming was still selling crankshaft kits for $2000. There also may still be some ECi cylinders that need to be replaced.

Lastly look at the airframe logbook for any damage, especially recent damage, that might have involved a prop strike. There are plenty of people who will dial the crank and leave it at that rather than do all the service bulletin work. Not good.