Is it time?

[Bill]

Background:

• Lycoming IO-360 in the Mooney 201
• Overhauled in 1996 by Mena Aircraft Engines in Mena, AK
• Right at 2000hrs
• Until this past weekend, a fully unremarkable service history, no issues with this engine.

Flying back from the holiday, partner noticed the oil pressure drop into the yellow, and at the same time #3 cylinder being 100*F lower on EGT compared to the rest of the cylinders. He made the immediate decision to divert and had an uneventful landing. Upon landing it was noted that the engine oil was low (3 qts.) with no signs of oil leakage on the engine externals.

A&P on field pulled the #3, and found the oil ring damaged and slight damage to the piston. Supposedly no damage to the cylinder. I have no pictures to verify. This A&P conversed several times with our home A&P, and they decided the best course of action is to replace the piston and rings, and then we will bring the plane home.

So, assuming the engine runs fine and get home, should we overhaul now, or with careful monitoring fly it another 2-300hrs? As said above, until now this has been a good running problem free engine.

 

[steingar]

Says me keep it running it and watch closely. Could just be one cylinder going bad and the rest can keep cranking for some time. I'd rather fly behind a 2000 hour engine than a zero time one.

 

[Ken Ibold]

Says me keep it running it and watch closely. Could just be one cylinder going bad and the rest can keep cranking for some time. I'd rather fly behind a 2000 hour engine than a zero time one.

I concur. Have you been doing oil analysis? Keep an eye on trends there, too.

 

[Bill]

I concur. Have you been doing oil analysis? Keep an eye on trends there, too.

Until now we had been doing 50hr changes with analysis, I am proposing to the partners that we drop to 25hrs with continued monitoring if we continue to fly the engine.

 

[Ted]

I'll be the odd man out on this one and say go ahead and overhaul it now.

You've found some issues with one cylinder. Might be isolated, but you'll put money into fixing this money that could go towards the overhaul. At TBO, you've probably also got other systems that are aging (fuel system, mags, etc.) and you can either work on those individual items or bite the bullet and do the full overhaul. Your resale value and potential market should you sell it go up with an overhaul, but they continue to go down as you keep flying it. For the first 400 hours or so your resale value doesn't change much with engine time.

These engines can start to nickel and dime you quickly as they get older, especially if you don't do your own work. On the 310 I ran the engines 400 past TBO, but my litmus test was that the first time I had to dig into something other than a simple accessory I was going to pull the engines and do them. There's lowest cost, and then there's best value. I tend to think that fixing your engine vs. overhauling it now is a lowest cost, but overhauling it is the best value.

 

[Bill]

There's lowest cost, and then there's best value. I tend to think that fixing your engine vs. overhauling it now is a lowest cost, but overhauling it is the best value.

If the plane were at home, I'd say yes, put the repair money towards the overhaul. But, the plane is 500nm from home, and that just adds way too much hassle and uncertainty having an unknown remote shop do a firewall forward. So, the repair will be done to get the bird home. The question is, then overhaul now or fly until the next issue?

And I see the flip side, if the next issue is 500nm from home, then you're doing the rinse repeat thing.

 

[Ted]

If the plane were at home, I'd say yes, put the repair money towards the overhaul. But, the plane is 500nm from home, and that just adds way too much hassle and uncertainty having an unknown remote shop do a firewall forward. So, the repair will be done to get the bird home. The question is, then overhaul now or fly until the next issue?

And I see the flip side, if the next issue is 500nm from home, then you're doing the rinse repeat thing.

Understood about not wanting to work on it 500 nm from home. Like you said, if it happens again like that you're doing the rinse/repeat. Obviously this is something I think about, too. On my St. Croix flights I was considering the possibility of an engine failure on the 414 that would result in me having to divert to a foreign country. Even landing in St. Croix with a bad engine would be an unpleasant option given the difficulty associated with getting a replacement engine down there.

 

[RyanB]

If you and the partners decide that an overhaul is in the cards, I recommend looking into Carlus Gann (Gann Aviation @ 9A5).

Good luck, Bill!

 

[Bill]

If you and the partners decide that an overhaul is in the cards, I recommend looking into Carlus Gann (Gann Aviation @ 9A5).

Yes, Carlus would be our 1st place to look, and likely who we'd use. He's just down the road and builds great engines.

 

[eman1200]

ugh, tough spot to be in

 

[Bill]

ugh, tough spot to be in

Really depends on if my medical comes through. If it does, I have no issues putting up my share of coin for a new engine. Actually, I won't be able to sell my share on a runout engine, so my decision is made either way. Damn, come on medical!

 

[SCCutler]

Assuming no internal damage, I'd install a new piston and rings and fly and watch.

Main thing that has me suspicious is, why the drop in oil pressure? 3 quarts low should not account for that, but perhaps that was enough less to allow for an increase in oil temperature and a concomitant reduction in pressure.

2000 hours on a Lyc 360 is hardly excessive.

 

[455 Bravo Uniform]

Sorry, couldn't resist, Bruce Buffer of UFC fame came to mind.

For me, it would be about peace of mind. I hate "waiting for the other shoe to drop" cuz I do it all the time.

 

[frfly172]

Change out the cylinder ,and motor on. Your A+P will let you know ,when he won’t sign off on the airplane ,without an overhaul.

 

[Stan Cooper]

Channeling Mike Busch, I'd say check the cylinder carefully for damage; if it's not damaged replace the piston and rings and soldier on, keeping a close eye on things. If the cylinder, including valves and valve seats, shows any sign of damage from the rings go ahead and replace the whole cylinder and piston assembly.

 

[mondtster]

What prompted the cylinder removal in the first place? I wouldn't have removed one on the basis of low EGT only. Also, besides the low oil pressure were there any other warning signs such as high oil temperature?

I'm no Lycoming engine overhaul expert but I've probably done a dozen or so in the last few years. I feel that running an engine too long prior to overhaul is a false economy. Unfortunately, every engine seems to be a bit different on how far you can go with it before you cost yourself more money than you save.

If this were my airplane I'd do what it takes to get the engine back together and get the plane home. After it's home I'd try to check the engine over as best as I could, and make a final decision. As long as nothing really bad was found I'd probably continue to fly the plane with careful monitoring, while I saved money and made arrangements for an overhaul.

 

[Skyrys62]

Not sure how the weather is down in SE TN during the winter...but if you see it as a low time flying period, it might prevent being down half the summer if something pops us again later.
Just a thought..

 

[UngaWunga]

No harm in pull the other plugs and stick in a scope to check out the valves like in another engine thread here. Can also check the plugs and pistons for oil burning. If the other cylinders look good, keep flying it.

 

[Brad Smith]

Did you check the oil level during the preflight before you took off on that last flight? The oil went somewhere and 3 quarts is a lot to account for...especially if you only suspect trouble with only a single cylinder. Did the technician perform a differential compression test of all the the cylinders? What were their values? I would be concerned where the 3 quarts of oil went on that last flight. It's possible that it could have pumped through only one bad cylinder or perhaps it had help. I remember an old pilot telling me that a premium overhaul on a Continental/Lycoming is about the same price as a decent funeral with burial plot and stone. He asked me, "Which is money better spent?" Hmmm....

 

[Lance F]

As you've just seen, an engine problem 500 miles from home is inconvenient and expensive. Without further information on where that oil went to so quickly and why the oil pressure dropped, I would overhaul.
I had Carlus Gann overhaul one of my TSIO520NB engines this year. Give me a call before you talk to him.

 

[mtuomi]

Yes, Carlus would be our 1st place to look, and likely who we'd use. He's just down the road and builds great engines.

Talk to Lance before talking to him.

 

[craigh]

I was in a similar situation the last couple of years. I ended up shopping around for an engine I could have overhauled and installed when the old one told me it was time. It could run another 1000 hrs. Mine just started leaking oil, the oil cooler was starting to have problems, etc. so I just pulled the plug and installed the new engine. Down time was less than 3 weeks including annual.

 

[edo2000]

Background:

• Lycoming IO-360 in the Mooney 201
• Overhauled in 1996 by Mena Aircraft Engines in Mena, AK.

I think you mean overhauled in Mena, AR.

I lived in Alaska for 50 years and never heard of Mena.

Good luck with your engine issue. It does sound like you have gotten pretty good service out of it the past 21 years.

 

[Bill]

I think you mean overhauled in Mena, AR.

Correct! My mistake.

 

[Bill]

I had Carlus Gann overhaul one of my TSIO520NB engines this year. Give me a call before you talk to him.

Wilco, Ted also gave me the heads up to talk with you.

 

[Ted]

2000 hours on a Lyc 360 is hardly excessive.

Keep in mind that Bill's Mooney has an angle valve 360, not a parallel valve. 200 HP vs. 180 HP. While they are still good engines and can (and often do) go past TBO, it's not the same as an O-360 in a 172 that you see routinely going to 3,000+ SMOH.

 

[UngaWunga]

Keep in mind that Bill's Mooney has an angle valve 360, not a parallel valve. 200 HP vs. 180 HP. While they are still good engines and can (and often do) go past TBO, it's not the same as an O-360 in a 172 that you see routinely going to 3,000+ SMOH.

What are the differences that cause one to last longer than the other?

 

[Ted]

What are the differences that cause one to last longer than the other?

The angle-valve cylinders have more airflow and make more power. More power = higher internal temperatures and pressures (significantly so) which accelerates the wear rate of cylinders, bearings, etc. Having a constant speed prop, the engine also makes a higher percentage power for a higher portion of time since it actually will achieve 100% power on takeoff (unlike a 172, which won't hit 2700 RPM on takeoff and thus not make full power).

It is possible for angle valve engines to have detonation occur, although that shouldn't happen if things are working correctly. It is virtually impossible for parallel valve engines to have detonation. If detonation occurs, that can more significantly wear components. The CHT rise and EGT drop that Bill described sounds like there might be detonation that occurred on that cylinder, which could have been caused by the broken oil ring allowing oil to get into the cylinder, which could increase the likelihood of detonation.

 

[Lance F]

My comment for Bill to call me was not meant to imply at all that he shouldn't strongly consider Carlus Gann for an overhaul. I did a lot of research before picking him. I just felt Bill could be better prepared for discussions with Carlus if he talked to someone with recent experience first.

 

[BillTIZ]

Get it fixed and get it home. Bore scope the other cylinders. How long to put another 200-300hrs?
I believe Lyc recommends overhaul at 2000hrs or 12 yrs. a 1996 overhaul is 21 yrs.

I think you said it was an O-360 and yes they are bullet proof, but if you do a lot of night or Long cross country, I would have an overhaul scheduled within the next year.

 

[Ted]

I think you said it was an O-360 and yes they are bullet proof, but if you do a lot of night or Long cross country, I would have an overhaul scheduled within the next year.

As I said, it's an angle valve IO-360, not a parallel valve O-360. The displacement is the same but there are a lot of differences.

 

[Bill]

As I said, it's an angle valve IO-360, not a parallel valve O-360. The displacement is the same but there are a lot of differences.

Is it harder to get angle valve cylinders? When looking at some shop web sites, they say rebuilds with parallel valve cylinders get new cylinders but angle valve versions get reman cylinders. Is this purely a pricing thing, angle valve cylinders are more expensive, or something else?

 

[Ted]

Is it harder to get angle valve cylinders? When looking at some shop web sites, they say rebuilds with parallel valve cylinders get new cylinders but angle valve versions get reman cylinders. Is this purely a pricing thing, angle valve cylinders are more expensive, or something else?

Parallel valve cylinders are available aftermarket, but angle valves are not. So your only options are either new OEM angle valve cylinders or rebuilt.

 

[Bill]

Parallel valve cylinders are available aftermarket, but angle valves are not. So your only options are either new OEM angle valve cylinders or rebuilt.

So, the engine is at ~4200 total time, and looking at the logs, these are 1st run cylinders. Some say if they pass inspection it's fine to reman and use 1st run again, what do you think?

 

[Ted]

So, the engine is at ~4200 total time, and looking at the logs, these are 1st run cylinders. Some say if they pass inspection it's fine to reman and use 1st run again, what do you think?

If those are original cylinders (which really makes them 2nd run, not 1st run, as they were overhauled) my opinion would be replace them. I generally consider factory Lycoming cylinders to be good for one overhaul. People can overhaul them more times, but that's where you get to the age where the cylinders will sometimes pop off.

That would be a consideration when comparing prices for a factory reman vs. basic overhaul.

 

[Bill]

I generally consider factory Lycoming cylinders to be good for one overhaul.

These were factory new cylinders at the last overhaul, but OTOH they're getting old. Things to discuss...

 

[Ted]

These were factory new cylinders at the last overhaul, but OTOH they're getting old. Things to discuss...

Ahh, ok. I misunderstood your previous post. So factory new at last overhaul, with 2,000 hours on them.

Like I said, I generally consider factory Lycoming cylinders to be good for one overhaul. In an ideal world, I recommend new cylinders at every overhaul. There's a reason why the OEMs and some of the bigger shops (such as RAM Aircraft) always send new cylinders on their engines - there's a better chance of getting to TBO without issue. Doesn't mean you won't get good service out of overhauled cylinders, but it's a consideration.

Personally I put new cylinders on when I overhaul engines on aircraft that need to work for a living. When we get our Cub to fly on our grass runway, I won't care so much about that. I'm also not sure if you can even get new cylinders for a C-85, I figure probably not.

 

[Tom-D]

It is only Time to overhaul when you think it is, every thing else is just numbers and opinions.

 

[Ted]

It is only Time to overhaul when you think it is, every thing else is just numbers and opinions.

True, Tom, but he was asking for opinions.

 

[mtuomi]

The angle-valve cylinders have more airflow and make more power. More power = higher internal temperatures and pressures (significantly so) which accelerates the wear rate of cylinders, bearings, etc. Having a constant speed prop, the engine also makes a higher percentage power for a higher portion of time since it actually will achieve 100% power on takeoff (unlike a 172, which won't hit 2700 RPM on takeoff and thus not make full power).

It is possible for angle valve engines to have detonation occur, although that shouldn't happen if things are working correctly. It is virtually impossible for parallel valve engines to have detonation. If detonation occurs, that can more significantly wear components. The CHT rise and EGT drop that Bill described sounds like there might be detonation that occurred on that cylinder, which could have been caused by the broken oil ring allowing oil to get into the cylinder, which could increase the likelihood of detonation.

Every time someone says "detonation" happens inside an internal combustion engine, a baby puppy dies...