Recommendations on oil consumption next steps

[vance.k]

Hey MS,

Would love to get some advice from the collective.  Have a 231 with a TSIO-360-LB1B.  It has 1,250TSN (2006).   I've put the last 600 hours on it over the last 2.5 years.   Until about 9 months ago, I would generally get between 8-12 hours per quart.  Starting around April, the consumption started increasing.  It increased rapidly and has fluctuated between 4-6 hours per quart.  Right when it started happening, my mechanic went through it, compressions, bore scope, etc.  Did not find a proverbial smoking gun.  Did the annual in August looked at everything again.  Compressions 78, 72, 77, 77, 70, 72.  Performance is consistent and hasn't changed at all.

Each time, there was some oil in several of the cylinders and the bottom plugs were dark, but the tail pipe is not oily.  There is a powdery trail on the belly behind the tail pipe.  

In September, I had an issue where the turbo seized.  It happened on the takeoff roll (out of Austin) and there were no indications of issues on the flight in or previously.  Coincidence?   I had hoped the rebuilt turbo would solve the mystery, but alas, no change.

There is some oil leaking from the pushrod tubes, the quick drain was leaking a bit (just replaced it), and there is some oil on the belly out the breather (and maybe 1 or 2 drips after shutdown).  I've had 4 different mechanics / IAs look at it while doing different work and everyone kind of shrugs and says none of them are bad enough to worry about, yet. Kind of a keep an eye on it and keep flying.

I'm working with a new mechanic (my previous one retired) and we changed the oil last week (and replaced the quick change to fix that leak).  We pulled the top plugs and grabbed some photos.  I wanted to get some additional opinions on these photos and recommended next steps.  Unfortunately, I didn't get any photos of the cylinder walls.

Thanks!
Vance

[EricJ]

Do you send your oil in for analysis?   That can be really useful when consumption starts changing, but it is most useful if you have a history of oil analysis against which to check trends.

 

[vance.k]

Hi Eric,

Forgot to mention it, but did attach a trend line chart from the analysis. I do oil analysis on every oil change, although totally spaced it on this one I just did. Got busy with the new mechanic and forgot to grab it.  Bottom line, nothing significant. No metal in the filter either.

Thanks!

Vance

[Andy95W]

12 hours ago, vance.k said:

 I've had 4 different mechanics / IAs look at it while doing different work and everyone kind of shrugs and says none of them are bad enough to worry about, yet. Kind of a keep an eye on it and keep flying.

 

I think those A&P/IAs are shrugging because your engine is pretty normal for a mid-time TSIO-360.  Needing a turbo overhaul at mid-time is also not abnormal.

You're starting to pick up some minor oil leaks and your cylinders are starting to get pretty oily, especially around your bottom spark plugs (such as the picture I included above). Certainly not abnormal behavior at mid-time as your oil control rings seem to be letting some oil past.  Your compression rings are still in nice shape, which is why your compressions are still so good.  Mike Busch would say the same as your mechanics, keep running it and feeding it oil until consumption gets greater than a quart every 4-6 hours, and keep borescoping the cylinders to see if one is getting considerably more oily than the others.  Mike would be against more invasive maintenance than that unless you absolutely had to.

If you really want to address the issue, then you'd be looking at a top overhaul, or at a minimum just putting in new rings.  That would also get all of the pushrod tubes resealed so they'd stop leaking too.  You might consider re-ringing the worst cylinders now, and then take another look at oil consumption in 6 months to a year and doing more, if necessary.  Done in conjunction with your annual inspection would keep the costs down.  I will admit that as an A&P myself, I'm better with Lycoming than Continentals.  @M20Doc and @kortopates could probably add better advice here.

I think you're lucky that you have so many mechanics that are looking out for you and not tying to screw you over.

[Gagarin]

Time after engine shutdown makes a big difference on measuring oil level. It takes at least a week for oil on top of the engine to drain down to the sump. It takes longer in the winter. High viscosity oil will take longer to drain. Wait at least a week for an accurate oil level reading.

[Guest]

The oily combustion chambers suggest worn rings and cylinder walls.  Higher static compression readings are a byproduct of excess oil on the cylinder walls and rings.  Oil seeps from the engine suggest higher blowby past the rings pressurizing the bottom end causing oil leaks.

Crankcase blowby can be checked per TCM Sb M89-9.

https://www.csobeech.com/files/TCM-SB-M89-9.pdf
 

Clarence

[takair]

What type of cylinders are you running.  Recently had similar on my Lycoming.  While my oil burn was never great it got dramatically worse over a short period.  Good compressions and borescope. Some oil in a lower plug, but oil got dark fast.  Long story short, I had older Cerminil cylinders and the compression rings had started to shed their molybdenum plating.  They were adequate for a compression test, but clearly leaking in operation.  

[vance.k]

Thanks everyone for the great pointers!  @M20Doc, thanks for the link.  I'm meeting the new mechanic out there this afternoon with an ASI and we are going to give it a shot!

As @takair mentioned, I had read repeatedly before that with blow by, the oil gets dark really fast.  I don't know that I've ever seen that quantified, but I will say I haven't noticed a dramatic increase.  I'd say it starts to get dark by 25 hours and I've been on a 50 hour interval when I'm flying a lot and closer to 35 when the bird has been sitting.  

Will update once/if we are able to get the ASI testing to work.  Thanks again!

[Mooney217RN]

Vance-

I am no expert, but I ran my IO-360 in my E Model to TBO with little issue.  Let me give you a couple of pointers from experience.  First off, change your oil & filter every 25 hours.  It is the cheapest insurance you can buy for your engine.  Second, if you can find any out there, do an oil change and use Exxon Elite 20/50.  It is no longer in production, but there is some out there.  I stocked up on a dozen cases that I have in my hangar, so I bet someone out there has some besides me.

I am not familiar with your engine, although I have flown the 231.  I now have an IO-550G in my Ovation.

You stated that "...the tail pipe is not oily.  There is a powdery trail on the belly behind the tail pipe.".  that's good.  You want a light gray/tan powdery trail.  that means you're leaning it out to the correct EGT.

Oil consumption is normal.  A quart in 25 hours is very normal.  If you're adding 3 quarts or more in 25 hours, you have a problem.  My engines have always consumed more oil at higher ambient temps than at lower ambient temps, in other words summer versus winter.  

[PT20J]

1. You were stable at 8-12 hrs/qt. The it rapidly changed to 4-6 hrs/qt. This means something changed in the engine, and it sounds more like a sudden change than a gradual one. 

2. You mention finding oil in several cylinders but you don’t mention which ones. Also, three have lower compression than the others. Is there any correlation?

3. You don’t mention excessive oil on the belly, so it’s not getting blown out. It must be getting burned. Paths to the combustion chamber are past the rings or the valve guides.

4. A problem with an oil control ring can cause oil consumption to increase without affecting compression. 

Skip

[carusoam]

Oil disappearing from a turbo engine has added opportunities to escape...

The pic of the plugs gives a hint that oil is escaping into the cylinders... where the plugs have dark crud on them...

That gives a hint of where to look closer...

If the cylinders are worn, they will be missing the cross hatching pattern that is pretty easy to see with the dental camera...

Really old cylinders that have run really hot can suffer from this wear...

The oil control ring is also a key place for an oil leak...

Check the age of the cylinders to see how many hours are on them...

Get pics of the cylinder surfaces.... look for smooth spots...

Oil is used as a coolant in the turbo... there are seals that keep the oil from escaping... along the shaft. 
After a bunch of hours... turbos get re-sealed and inspected for wear... in some turbos, it is easy to see into with the dental camera...

Getting a turbo resealed doesn’t cost too much... compared to finding turbo blades that are only nubs... that becomes an OH...

It really helps to have somebody watching during start-up... that much oil might have a brief smoke show related to start-up...

The other place to look for oil escaping... is the valve guides... oil has a tendency to sneak past the seals when things wear... the test for this... is called the wobble test...

I am missing something from the pics...?   The K has a six cylinder engine... where are all the bottom plugs? When looking for oil contamination... the bottom plugs are usually the ones to suffer the most...

PP thoughts only, not a mechanic...

Best regards,

-a-

[jlunseth]

I have a 231. I am closing in on 1200 hours flying it.  I went through a similar trajectory during the first few hundred hours and reached the point where I needed a quart at about the frequency you are at right now.  I heard and read the advice that it is normal, etc.  Then we found the leak, the quick drain wasn’t sealing because of debris, and one night we blew all the oil out of the engine.  I managed to save the engine (I wasn’t thinking that way in the air, but that’’s how it worked out).  I got the quick drain problem straightened around but was still losing some oil, we kept looking for leaks and there were frankly quite a few sources, the rocker covers in particular, we tried new rocker cover gaskets and that did not help much. We decided the engine had suffered some ring slap when I made the emergency descent due to the quick drain.  The engine was sent to Bolduc in Anoka and IRAN’d.  They did a fabulous job.  It came back running more smoothly than a 231 engine deserves to run and has stayed that way.  I need about 1 quart between oil changes at 25 hours, and the engine currently has nearly a thousand hours on it since the IRAN.  I see you changed the quick drain, so that is not it hopefully.  One recommendation I make to everyone who will listen, is to have the quick drain pulled at annual and let the oil drain out of the big hole.  The debris that jammed mine was a very small but long sliver of some kind of plastic.  Then install a quick drain “kit” so the thing is sealing again.  I realize this probably is not your issue. I have been running LOP most of the time since that incident and that may help to account for the better health of my engine.  But the moral of the story is that the 231 engine, when healthy, does not burn much oil.  You might get the air/oil separator cleaned also.  They can get gunked up, and if the engine can’t breath it blows oil out any available orifice. 

4-6 quarts tells me that you have at least one leak source somewhere, they can be very difficult to trace because the air is moving around in the engine compartment and tends to blow oil everywhere.  I had oil weeping out of the fiberglass of the cowling for several years after the leak was stopped.  IRAN was about 7,000 but was the best thing I ever did for my aircraft, the engine was an accident waiting to happen. The turbo had nothing to do with it BTW, I had the turbo OHd when I first bought the plane and am still running the same turbo with negligible oil loss.  Exhaust pipe is dry.  

When you pre-flight, do you have any drips at all on the tarmac?  I don’t even get dripping out of the breather tube, but that would not worry me.  Anything anywhere else would be a concern.

[vance.k]

Hi Everyone,

Just a quick update.  @M20Doc, we were able to do the pressure test using an ASI according to the TCM SB.  At full power, with or without the breather system attached, we'd get fluctuations between 95 and 105 mph.  So, according to the SB, that is above the 'ground limit'.  So, stands to reason that is related.

I'm curious, though, does anyone know what the 'normal' value is for a healthy TSIO-360?  I imagine most people don't do this test until troubleshooting a problem.  The SB doesn't really provide guidance, just that 90 is the limit on the ground.  Ultimately trying to understand if that is 'the' smoking gun or if those values are 'marginally out of bounds' but may not be the whole issue.

Someone asked which cylinders are oily.  To my eye, I believe 4 out of the 6 are oily.  I'd say they go in order from worst to best like this; 6, 2, 4, 1, 3, 5.  I'd say 5 has no oil, 3 maybe a touch.  Any idea if there is any significance to all the evens being the worst ones.  We didn't pull the bottom plugs, except cylinder 1.  We were getting decent enough borescope photos to be able tell the plugs were oily.

 

Also curious about another oddity, although I suspect it is a red herring.  When the ASI was connected but the breather system was still attached (including the oil/air separator), when the engine started, the airspeed would jump between 20-40, but then at idle, would setting around 5.  Once I started applying power, it would pull to 0 and stay there, as if there was a vacuum applied.  We did it a couple times thinking something wasn't connected right before finally just going full power and as the power got past maybe 30", the ASI jumped to life.  When we disconnected the breather and reran the test, it didn't do that.  It stayed around 40mph at idle, but once I went full power, it had the same 95-105 range.  

So, based on this, what next?  Re-ring (all cylinders?), top overhaul, IRAN the whole engine?  

Thanks, really appreciate the help!
Vance

[Guest]

There will be some fluctuations in the ASI during the test, you can install a snubber in the line to smooth it, or  you can use a water manometer.  If I recall correctly, 90 mph equates to 4” of water. Double the mph, square the water column, the pressure rises rapidly.

Clarence

[WilliamR]

So, I've been down this exact road with a TSIO-360MB with about the same time.  Followed the SB and sure enough, good amount of blow by.  This was also affirmed with minor air leakage out the filler tube, not the exhaust and a fair amount of oil out the breather (even after fully cleaning the breather).   

Summary: I changed the three oily cylinders. After the change, oil consumption and quality greatly improved.  Oil at the breather also decreased.  I didn't change the remaining cylinders because they looked pretty good.

Advice: First, I'm not an A&P but have wrenched for shops when younger and am very hands on.  I would replace the 4 most offending cylinders only.  Replacing gives you new things like rings and new x-hatch on the cylinders.  Re-ringing will not fully fix the problem if there is also no x-hatch in the cylinder (likely).  You could fully top with the assumption that as the first four cylinders go, so will the others.  The flip side of that coin is why fix that which is not broken.  You could IRAN, but this seems to be a cylinder problem not a bottom end problem.  Conti bottom ends seem to do pretty good in my experience.

Btw, exhaust valves look very nice.  Guessing you run ROP.  Not trying to start a fight either way, just an observation given the deposits on the valves and cylinders.

William

 

[carusoam]

Nice pizza patterns... indicating good valve health.  
 

Not odd, non-circular patterns that would indicate a sticking valve...

-a-

[exM20K]

When my 231 got to that level of oil consumption, oil was very evident on the belly and the tail tie down ring.  It is a lot of oil.  So if it is getting burned up, I’d check the turbo seals and get a good look at the cylinder walls.  While it’s unlikely that the walls are glazed at 1200 hours, there could be one or more that have surface corrosion, which would account for the oily plugs and consumption.

-dan

[Pete M]

Run some mmo through it (check turbo compatibility) to clean up/ unstick the rings then try some camguard. See if it improves. Must borescope the cylinder walls. Clean up all your leaks. You could also try a straight weight oil with camguard. Monitor and change oil when it gets dirty. I wouldnt consider spending a ton of money on an engine burning a quart every 5 hours. Once oil consumption stabalizes I'd change it more frequently, especially if you're getting some blow by. . Doesnt make sense to spend 8k to save a few quarts of oil. Save your money for overhaul. You're on the back third of its life. I recently priced overhauls on that engine. Their approaching 40k. 

[Mufflerbearing]

I was wondering when the MMO comment would show up in this discussion. 

I have used it and I like it.  I think it works well for certain things like sticky rings and such.  However, there is never a thing called a mechanic in a can.

[MooneyMark]

Folowing with interest, what does one do if you have your engine IRAN’ned? Send it over to the ayatollah?

[Pete M]

...who will bless it according to the dictates of mohammed, cover it in palms and dates and then send it back to you. If it fails, it was simply the will of Allah. Be at peace my brother.

[N201MKTurbo]

As-salāmu ʿalaykum