Cylinder woes

[flyboy]

I am going through oil like mad, about 1 quart in two hours in my O-360. It looks like most of it is going through the breather and then on the belly. TSMO 1930, was done in 1985. #3 has 700 hours on it, all other cylinders have 1920 hours run time per the engine log. Is it normal for the induction tubes to be wet with oil on the inside? I am sure this part is due to worn intake valve guides. This would explain some of the oil loss, however the oil lost through the intake valve guides would end up in the combustion chamber and burned. It doesn't seem to me that this explains any of the loss through the breather. Compressions are #1-78, #2-76, #3-78, #4-78. Engine runs great, just using oil. I normally say "oil is cheap", but this is getting painful.

 

Pulled #2 cylinder due to minor leak at base of cylinder, found induction tube wet with oil on the inside and a bit of oil dribbled out of spark plug hole. Piston and rings look great. Valve guides have some wobble, but not bad considering the time on the cylinder. Going to replace oil ring, valve guides and all gaskets. Currently waiting on parts. 

 

Pulled induction tube off of #4 today, wet with oil inside, no dribble from plug hole.

 

Should I pull #4 as well? Your thoughts?

[carusoam]

1) What causes things to leak out the breather???

Case pressure comes to mind...

2) What causes case pressure???

Leaky rings...

3) what causes leaky rings???

Wear or breakage...

1 qt per 2 hours is excessive. It shouldn't be hard to identify the culprit.

4) I would consider seeking professional help, expecting that the mechanic will recomend compression testing...

He will probably be listening for air leaking past valves or possibly sending a camera down the spark plug hole. Finishing up with wobble testing.

He will probably suggest overhauling cylinder assemblies after they are determined to be worn.

Or save the small dollars on this and move towards OH????

Your engine is Old, calendar wise...

Your engine is high time, hours wise...

But, you knew this already...

What else is in the induction tubes?

1/8" blue goo. All four are typically loaded the same way. Oil isn't normally in there.

5) what causes oil to leak into an induction tube?

Intake valve comes to mind. But that would have to occur on shut down or something really odd.

Oil analysis is a low cost method to possibly determine what is wearing or is broken.

Sounds like low cost is important to you. Safety of flight should be weighing on your decision making.

My M20C experience...

Non-professional opinion,

-a-

[N33GG]

Not exactly the same situation, but last year I was having similar issues. Instead of fighting cylinder by cylinder, I opted to have all four replaced with factory new assemblies with new pistons. Not exactly cheap, but the difference is amazing. Solid power with no "morning cough", and oil consumption is less than a quart every 10 hours. Glad I did it.

You makes yer picks, and you takes yer chances.

Good luck!

YMMV and FWIW, as always...

[cliffy]

Unfortunately you are looking at near 30 years on an overhaul (that's a long time), 70 hours to overhaul time hrs wise (if you follow the 2000 TBO), and having to put money into an engine right near pull apart time. 

You can patch the cylinders with some work but you need to decide how long you are going to run this engine. Do you want to go to 2200 hrs? Then you have to amortize what you spend now (and what may happen in the near future) on those 200 hrs. No requirement for you to overhaul at 2000 hrs but how much do you want to spend now before you do. 

At 2000 hrs in 30 years your're looking at around 5 hrs per month for its lifetime. Has the engine ever sat idle for months at a time in these 30 years? That means rust inside on the cam and lifters is a possibility. That means more wear in its lifetime. If I were you, with the current issues and the total life this engine has had, I would be looking for an overhaul shop. You've gotten your monies worth out of this engine. It's time.

[N201MKTurbo]

Do a compression check on each cylinder. Listen to the oil fill tube to see which cylinder has the most blow by. If they are all the same then live with it til overhaul. If one has a lot more then the others, then fix it.

[larryb]

My theory of airplane ownership, as well as other things, is to minimize lifetime costs. That often means pay now to fix it right vs. spending $ on a patch job now only to have to fix it right in the near future. Your engine is talking. I would listen before it talks louder. I believe it's time for a full overhaul. I would not feel comfortable flying behind that engine.

 

Larry

[MB65E]

On cylinder 2 just make sure the case is not cracked by the lower left cylinder base stud. Ours was, impossible to see on the ground with the gray oily paint. Previous shop had the jug off changed the o-ring and still missed the crack. I'm convinced that the Lycoming IO-360 cylinders will show 80/80, have shot valve guides, and ready to just about to fall off the engine...

Our Cam was shot too at 1200hrs on an '85 overhaul. THE only components that were saved was the Crankshaft, 3 rods, all hyd tappets, lower sump, and intake tubes, and data plate. Everything else was scrap. That was literally the best running piece of Garbage I've ever flown...Until we found the crack in the case!

Good luck, you might be able to get a salvaged IO-360 from some where for about $8-10k with around 1k hrs on it. Looking back, that would not have been a bad option. All depends on what type of project you want. I did everything my self, sent out all the parts, worked with a cylinder shop on overhauled cores and came in at about $15k. Only took a year...

I had a great quote for $23k from an excellent engine shop I've worked with, hard to make money these days on engines. No regrets! It was a fun project that opened my technical abilities.

All the best!

-Matt

[Lood]

Although they are high time in terms of years, your cylinders are still in their first life and I presume that they're still standard? If so, you might investigate having them cut to +.10, re-honed and new over sized rings fitted. This is quite common practice here in SA, it is not very expensive and if done properly, these cylinders may run for many more hours.

Do check that crank case for cracks though.

[MB65E]

Good point, that is pretty low on the heat cycles. Doesn't hurt to pull the cylinders and have them checked out. If you are able to repair them they should last till the bottom end or cam starts to make metal. That would be the most cost effective, unless you had a budgeted for an overhaul of the engine in a few hundred hours or so. The oversized pistons are hard to find I was told...

-Matt

[robert7467]

Check all the tubes, mine was rubbing all over aluminum sheet metal. You want to make sure they are all free from rubbing. The tubes cost about $200 from lycoming, or you can buy some aluminum brazing rods from tractor supply to fill in the hole. The lower tubes are for drainage and have no pressure running through them, so brazing is acceptable.

[N601RX]

The best course of action may be determined by the labor rate you are having to pay. If your paying $80 hr then a patch job may not make much sense. However if your doing the work under the supervision of an AP and the labor cost is low, then a cylinder touch up may be a good option.  I would be a little hesitant to replace the oil ring only. I would think it would be better to hone the cylinder and replace all 3 rings, a ring set doesn't cost that much and the labor would be the same.  I would also consider going ahead and doing all four with the plan to fly if for another 400hrs or so if everything else was good. 

[Ron McBride]

I did a top overhaul on mine a couple of years age.  I had cylinders that were .010 oversized and going thru oil, quart every 2 or 3 hours, black within 10 hours. My mechanic kept saying, you are ok, it is not worth the money. All compressions were in the 70's. The cylinders were shot, the choke was gone.     I bought used first run from Lycon for about $1,200.00 each and installed them under supervision. I had my mechanic inspect the cam and lifter while I had it apart.  They were great, if bad I probably would have done a field overhaul.    Now oil use is a quart every 10 hours plus.  I am very happy with this, and a lot less cleaning of the belly.

 

Ron

[N33GG]

Not exactly the same situation, but last year I was having similar issues. Instead of fighting cylinder by cylinder, I opted to have all four replaced with factory new assemblies with new pistons. Not exactly cheap, but the difference is amazing. Solid power with no "morning cough", and oil consumption is less than a quart every 10 hours. Glad I did it.

You makes yer picks, and you takes yer chances.

Good luck!

YMMV and FWIW, as always...

To add a couple of points... My engine too was OH'd several decades ago. The first step was to pull all four cylinders and have Don Maxwell give the cam lobes and inside of the case a good look. Everything looked great, so we ordered the new cylinder assemblies.

I was prepared to make the OH choice if anything looked questionable.

[aaronk25]

Assuming a borescope inspection shows all cylinders with abnormally high oil consumption I'd probably pull all the cylinders and send then to ECI to be plated. If the cam or lifters looks worn I'd overhaul the engine, if not bolt the repaired jugs on run it another 1000 hours as is with frequent oil analysis monitoring....my thoughts.

[Mooneymite]

Unfortunately you are looking at near 30 years on an overhaul (that's a long time), 70 hours to overhaul time hrs wise (if you follow the 2000 TBO), and having to put money into an engine right near pull apart time. 

 

The decision to ignore TBO is based on "condition inspections" at each annual.  Whether we overhaul at some point beyond, or short of the manufacturer's recommendation is contingent on various parameters such as compression, oil consumption, oil analysis, etc.

 

Without knowing much about your engine, I'd say that your engine is displaying warning signs such that a thorough, close and critical evaluation be made by a knowlegdeable engine person.

 

Doing a "top" may just be treating the symptoms of an engine about to fail.  But we're speculating.

[Jerry 5TJ]

Oil 'consumption' in these Lycoming engines is strongly dependent on static oil level, too.   You did mention most of the oil is going out via breather.

 

If you're not already starting short flights with the oil at about 6.5 quarts and then adding 0.5 qts at a time to keep the level between 6 and 6.5 on dipstick you might try that and monitor the consumption.  

 

My plane's O-360 uses about 0.5 quart in 6 to 8 hours if I start at 6.5.   If I fill to 8 quart level on the dipstick it blows out a quart in the first hour or two.  Then it takes another 2-4 hours to go from 7 to 6.5 quart level.  

 

[MARZ]

4,800 to go from a quart in two hours to a quart in ten. If the engine isn't pending failure I'd recalculate that roi.

Sent from my iPhone using Tapatalk

[cliffy]

Jerry does make a good point about oil level vs oil usage. 

[scottfromiowa]

I elected to overbore our first run cylinders at overhaul vs. replacing. 500+ hours and going strong...

[KSMooniac]

I did an IRAN on my 4 cylinders at 1650 SMOH using my labor with supervision, and got them all freshened for $2200 including new pistons.  That got me another 500 hours before I lost a cam lobe and I am happy with extending my engine life for that price.  (I'm not happy about losing a cam lobe and lifters!)  All we had to do was hone the cylinders so they didn't get oversized, thankfully.  I just got them overhauled in conjunction with my engine overhaul, and again they are still standard size.  Angle valve cylinders are expensive, so I elected to overhaul them since they were first-run.  YMMV.

 

At 2000 hrs and nearly 30 years, I think it might be false economy to just address the cylinders without going through the bottom end, though.  Removing all of the cylinders is more than half the work IMO, so why not go ahead and split the case and inspect everything else?

[N33GG]

Oil 'consumption' in these Lycoming engines is strongly dependent on static oil level, too.   You did mention most of the oil is going out via breather.

 

If you're not already starting short flights with the oil at about 6.5 quarts and then adding 0.5 qts at a time to keep the level between 6 and 6.5 on dipstick you might try that and monitor the consumption.  

 

My plane's O-360 uses about 0.5 quart in 6 to 8 hours if I start at 6.5.   If I fill to 8 quart level on the dipstick it blows out a quart in the first hour or two.  Then it takes another 2-4 hours to go from 7 to 6.5 quart level.  

Ditto here. If I fill to 8 quarts, I think my plane dumps the first quart on the take off roll.