Years Between Overhauls

[Northernboy70]

I am looking at purchasing a plane with low engine hours but the last overhaul was done in 1990. According to Lycoming if TBO has not been reached in 12 years it should be overhauled even if the hours are not up. I am wondering if this applies, should it reduce the price since an overhaul should be done.

Thanks

[cgzro]

The problem with a Lycoming with low hours and lots of years is rust.
If it does not fly every week or so the camshaft and/or lifter faces will rust then you will get some spalding where the camshaft hits the lifters, that will shower the piston skirts with metal which will then scrape it down the sides of the cylinders which will then lead to plug fouling which will lead to ... etc.

If I were buying a Lycoming with lots of years but few hours I'd make pulling he #1 cylinder part of my pre-purchase agreement to check the lifter faces and camshaft for problems. It only takes a few hours to get it on/off and if you find a problem you will have saved yourself 10's of thousands of dollars. You should also look under the rocker covers to make sure there is no rust there either, although a new cylinder or rebuilt one is peanuts compared to splitting the case. Obviously pulling the oil screens and looking for metal, an oil analysis etc. are pretty important too.

Having said that I think its only Lycomings recommendation, very few owners actually rebuild a perfectly good/working engine at 10 years.

Peter

[corroded_camshaft]

The aircraft I purchased in 2005 had at the time around 280 hours on the engine, the overhaul being done in 93. Cylinder wasnt pulled during pre-purchase though, I didnt think about it. I still havent overhauled the engine but this past annual, I had to get it repaired.

The AME (likely) broke a stud which forced him to remove a cylinder. He found corrosion on the pushrods, lifters, and camshaft.

I took the engine to Aero Atelier in Quebec and had them do the repair. The initial 'over-the-phone-quote' was for about 3500 dollars, including labour to take the engine completely apart, and regrounded camshaft, lifters, and new pushrods. When I got to the shop and they tore the engine down though, that change drasticly. New piston rings were required for all four cylinders, and on a 235, those arent cheap. A new oil pump gear too, though that was peanuts. I also opted for new rather than reground.

The pushrods were bright orange rather than black, from corrosion, the lifters seemed ok but a few stopped turning and were being hit by the cam always at the same place. Even the cam didnt look as bad as my AME said. A bit of pitting in the lobes but the shop said they could get it reground and put back in. Still, went for new (got to keep the old cam and other parts)

Aero's labour was 2500 dollars. That included complete disassembly of the engine, cleaning, reassembly, and painting. Not too bad. But still expensive.

I was charged 5.75 hours to remove the muffler, engine, accessories, from the airplane to send it out, and 16 hours to reinstall.

That adds up big time too.

That being said, this was just a repair and not an overhaul. So Im still at around 2020 from TBO. When Aero ran the engine on the bench, they told me they were surprised by how good the engine performed and how good the compressions were already. They said so long as I take care of the engine (which of course, is the plan, unlike previous owners who've let it sit a combined 13-14 years!) I'll likely be able to reach TBO.

[Northernboy70]

Thanks for your feedback I will ask to check for corrosion before closing the deal. Just wondering if the value would be less because of the years between overhaul. I am just worried that when I goto sell the plane and it is not at the TBO but 25years since overhaul will I take a loss?

Thanks

[black hole]

As corroded_ cam said :The engine for private use does not have to be overhauled. A tear down and repair can be done for a fraction of the overhaul price. but I do agree with pulling a cyl. before purchase.

BH

[iflyforpie]

According to CAR 625 APP B, engines that have been out of service for 12 months require an internal inspection. My interpretation of this would be to borescope all cylinders and pull a jug from each bank to examine the crank and cam.

There are no other legal limitations for private operators, including TBO, as long as you as a pilot feel comfortable flying it and your AME is comfortable signing it out. I've seen engines in service with over 30 years SMOH (flown regularly but low hours) and running fine.

[CpnCrunch]

There are no other legal limitations for private operators, including TBO, as long as you as a pilot feel comfortable flying it and your AME is comfortable signing it out. I've seen engines in service with over 30 years SMOH (flown regularly but low hours) and running fine.

Yes, that's the key - FLOWN REGULARLY. That is much more important than last overhaul time or hours. Anything less than 5 hours per month is considered "inactive" according to Blackstone Labs. If it has been sitting idle for long periods of time (like most private planes seem to be), don't touch it unless you can be certain there is no corrosion.

A lot of owners seem to think it's fine if the engine is below TBO in terms of hours, but they don't seem to care that it was overhauled 30 years ago! However if you are buying a plane you should certainly consider both when deciding whether or not to buy a plane, and when calculating the price.

[twotter]

And we care about Blackstone labs because????

If it has been inactive in needs an internal.. If it hasn't been overhauled, lycoming or continental, they both recommend it at 12 years for a reason..

[CpnCrunch]

And we care about Blackstone labs because????

They say that because they start seeing corrosion in the oil if the plane has flown less than 5 hours per month. Obviously not as bad as leaving the plane for a whole year without flying and without pickling, but that is the yardstick they use and they are the people who actually measure the corrosion in your engine!