Top Overhaul of Not?

[Bob - S50]

Looking for opinions.

We switched oil from w100 to Phillips 20w50 XC and thought we had a consumption/leak problem.  Went through a quart in about 2 hours.  Got oil on the door and even a little on the left wing route root.  No leaks found.  Since then we are back to our normal 5 or 6 hours/quart.  We only fill to 6 quarts, even with the new oil.  Ever since we got the plane, the oil gets dirty very quickly, within just a couple hours.  With the combination of oil use and excessive blowby we were planning on doing a top overhaul with the annual this September.

• The engine was new back in the mid 80's when it replaced the original after it threw a rod.
• It now has about 1100 hours on it.
• Oil consumption is back to a quart every 5 or 6 hours.
• Oil is dirty within 2 or 3 hours of an oil change.
• Airplane sat unused for 10 years in a hangar in Northern CA before we bought it.
• Borescope looks normal, no excessive wear.
• Oil analysis is all normal, not making any metal.
• Flys great!

I'm thinking we have excess blowby because, after 30 years, the rings are tired and not pressing hard enough against the cylinder wall.  I think I've read somewhere that excessive blowby indicates a top overhaul is warranted because of all the nasty stuff that happens to the oil.

Here's the question.  Would you do a top overhaul because of excessive blowby?

Edited April 26, 2016 by Bob - S50
wrong word

[MB65E]

Check the compression. Then I would run mineral oil in it and run it as hard as you can for an oil change or two. I would increase the oil changes,  say 10-15 hours this will keep the oil fresh from blow by contaminants. Do this for a bit until it stabilizes again. A friends io360 had 2 of 4 cylinders with broken rings. It really used some oil...But,  If you say you are already back to 1qt in 5 or 6 hours.  I'd leave it alone for a bit longer. Throw some cam guard or avblend in there if it makes you feel better. If you befriend your IA and a local engine shop I have seen new rings and honing for less than two grand.

However, when you pull the cylinders, you will probably find things that are fine but should be fixed. It's a bit of a can of worms with that old of an engine that leads to an overhaul. Our 1200hr io360 was the best running can of worms I had ever seen or flown. It's oil would turn black after 3hrs. 78/80 compression, crack in case, 3 of 4 rods excessive corrosion, shot 2 piece cam, worn crank gear, rusted acc gears, 2 of 4 cracked cylinders, worn piston pins, and the list goes on. 

Good luck!

-Matt

 

[Yetti]

Compression check should find the offending cylinder or two.   R&R that cylinder

[Bennett]

My J started burning oil at an unacceptable rate: 1 quart every two hours or so, and the oil was black within two hours after an oil change. No leaks under the cowl, clean belly, no wetness in the exhaust pipe, great compressions (tested several times on different dates), and so I had LASAR remove one cylinder to inspect it. Black everywhere inside, but otherwise nothing obvious. They did note that the cylinder was chrome. There was about 600 hours since the engine was overhauled, and I decided a top overhaul would be prudent. (Yes, I know the Busch arguments against doing this.). LASAR removed all four cylinders and sent them out to an engine shop for further evaluation. In the meantime LASAR flushed the engine and oil cooler to remove all the "blackness". The cam was perfect. Hooray for that! The engine shop bought new nitrated cylinders, ground the valve seats, replaced one piston, and reinstalled all my old parts (once cleaned and checked), new rings and piston pins, etc. LASAR reinstalled the cylinders and flew the initial break-in hours. All is great now, and after 6 hours the (mineral) oil is as clean as it was when poured in. I'm glad I had the Top done. I'll have the oil changed at 25 hours. The cylinder work cost was reasonable, and I would do it again in the same circumstances.

[PaulB]

Excessive blow by may also be from a crankcase seal leak.  The sump gets pressurized from ram air and the oil mist is then blown out the breather tube.  If you've got good compressions you might look at that.  Doesn't really explain the dark oil though.  I'd also avoid replacing all the cylinders at once.

[Yetti]

3 hours ago, Bob - S50 said:

I'm thinking we have excess blowby because, after 30 years, the rings are tired and not pressing hard enough against the cylinder wall.  I think I've read somewhere that excessive blowby indicates a top overhaul is warranted because of all the nasty stuff that happens to the oil.

Here's the question.  Would you do a top overhaul because of excessive blowby?

So what changed?   It was doing fine running W100.  Have you switched back to W100? which technically was what the engine was designed to run on.  I mean the engine has a breather tube on it... how close of tolerances could there be in the engine?  So now you have a thinner oil and it is slipping past those gaps....

[carusoam]

A bore scope may give you some insight to what may have happened to the cylinder's surfaces during it's long slumber..

Talk with your mechanic to see if he can get some pictures of each cylinder.  Start with one to save costs...

If you find the nice diagonal machined hatch marks have been replaced with deep pock marks or are worn smooth.  Go to Bennet's post (above) and re-read what he did...

Logic: If rust formed deeply into the cylinder surface, it can cause some wear to the rings as well.  Ring wear + non-ideal surfaces can cause blow-by.

Logic 2: if the W100 oil works better than the less viscous/thinner go back to that again.

Logic 3: a complete changeover of oil may be necessary to obtain the higher viscosity.  It won't work one quart at a time.  It also may not be completely changed until a second oil change flushes most of the thinner oil out.

Logic 4: If you find that new rings are needed and resurfacing the cylinders would be helpful.  That probably defines the desire for a Top Overhaul. 

Get a good look at the valves while you are in there...

Private pilot ideas. I am not a mechanic.

Best regards,

-a-

[DXB]

20 minutes ago, Yetti said:

So what changed?   It was doing fine running W100.  Have you switched back to W100? which technically was what the engine was designed to run on.  I mean the engine has a breather tube on it... how close of tolerances could there be in the engine?  So now you have a thinner oil and it is slipping past those gaps....

I don't get why W100 vs 20W50 would make a significant difference in the amount of blow by - aren't they the same viscosity at operating temperature (ie. SAE 50)?   I'm not doubting the OP's observation - in fact I also seem to consume more Phillips XC 20W50 in the winter than Aeroshell W100 in the summer, I just don't have a clue why.

[Piloto]

Bob you have a dirty sump.

For cleaner oil on the stick this is what I do at every oil change:

1. Drain the oil one week after last shutdown. This assure all the old oil in the upper parts of the engine is drained down to the sump.

2. After all the oil has drained I close the drain valve

3. I pour one gallon AVGAS into the sump. And leave it stand for at least half hour. AVGAS will mix with the residues in the sump. Meanwhile I replace the oil filter.

4. Using a clear drain hose I drain the AVGAS completely. At first the color of the drain is black (residue) and then turns clear. 

5. After AVGAS is drained I pour in 8qts of Aeroshell 15W50.

Using the above procedure the oil remains clear up to about 40 hours. Above 40hrs it turns light brown but you can easily see the dipstick marks. One minor problem I have is that during the first 20 hours the oil is so clear that is hard to see the actual level on the dipstick.

On my IO-360 with the M20 oil separator it burns 1qt every 10 hours when filled to 8 qts, and no belly mess.

I have done the above procedure on three engines. All made it to TBO with high compressions and low oil consumption.

José

Edited April 25, 2016 by Piloto

[carusoam]

Dev,

I think the difference is the two oils are the same in a test device under test conditions.  In reality, they are being challenged in the real engine under real conditions.  Adding wear into the mix adds more challenges.

a blend of long chain molecules with short chain molecules can duplicate the viscosity of a quart of medium chain molecules under an ideal set of conditions...

But, they won't be the same under all conditions...

PP ideas, with a blend of polymer rheology background...

Best regards,

-a-

[ArtVandelay]

Bob you have a dirty sump.

For cleaner oil on the stick this is what I do at every oil change:

1. Drain the oil one week after last shutdown. This assure all the old oil in the upper parts of the engine is drained down to the sump.

2. After all the oil has drained I close the drain valve

3. I pour one gallon AVGAS into the sump. And leave it stand for at least half hour. AVGAS will mix with the residues in the sump. Meanwhile I replace the oil filter.

4. Using a clear drain hose I drain the AVGAS completely. At first the color of the drain is black (residue) and then turns clear. 

5. After AVGAS is drained I pour in 8qts of Aeroshell 15W50.

Using the above procedure the oil remains clear up to about 40 hours. Above 40hrs it turns light brown but you can easily see the dipstick marks. One minor problem I have is that during the first 20 hours the oil is so clear that is hard to see the actual level on the dipstick.

On my IO-360 with the M20 oil separator it burns 1qt every 10 hours when filled to 8 qts, and no belly mess.

I have done the above procedure on three engines. All made it to TBO with high compressions and low oil consumption.

José

1. A week sounds excessive to me, I'd bet 24 hrs would be enough.

4. How do you insure it drains completely? Deflate the nose tire?

5. I'm surprised you don't use 100 here in south Florida?

If you are really anal...add a few more steps:

6. Run engine to dilute whatever dirty oil is still in the engine (most probably in the oil cooler, and maybe the prop).

7. Drain and refill. You now have superclean oil throughout the engine.

Maybe use Marvel mystery oil in step 5 to clean it out.

[N601RX]

5 or 6 hrs a quart isn't bad.  Oil is cheaper than cylinders.

[Ratherbflying]

8 hours ago, Bob - S50 said:

Here's the question.  Would you do a top overhaul because of excessive blowby?

No. Spend the money on an Engine Monitor.

[jetdriven]

5 hours ago, PaulB said:

Excessive blow by may also be from a crankcase seal leak.  The sump gets pressurized from ram air and the oil mist is then blown out the breather tube.  If you've got good compressions you might look at that.  Doesn't really explain the dark oil though.  I'd also avoid replacing all the cylinders at once.

You're saying that ram air pressurizes the crankcase from air blown into the front of the engine via the nose crankcase seal?  No way, that's ridiculous.

[PaulB]

16 minutes ago, jetdriven said:

You're saying that ram air pressurizes the crankcase from air blown into the front of the engine via the nose crankcase seal?  No way, that's ridiculous.

I'm no expert but that's what Mike Busch says.

[Yetti]

18 minutes ago, jetdriven said:

You're saying that ram air pressurizes the crankcase from air blown into the front of the engine via the nose crankcase seal?  No way, that's ridiculous.

It's possible if for say you maybe left the dipstick unscrewed back into where it goes.... not that I would know that condition

[Guest]

TCM has an SB on crankcase pressure limits, 4" H2O or 90 mph.  Lycoming has no such limit.  Recently we removed a cylinder from a customer's IO 360 which had dirty ish oil and a dirty plug, it had a corroded cylinder wall.  

Crankcase pressure showed no reading on this Lycoming, it seems meaningless.  After a replacement cylinder was installed the oil stays clean, consumption in way down, both the engine and owner are happy now.

Cylinder compression readings can be tricked by excess oil above the rings.

After trying Jose's cleansing of the engine oil sump, I'd also flush the oil cooler if the oil still gets dirty the writing is on the wall for cylinder work.

Clarence

[jetdriven]

1 hour ago, PaulB said:

I'm no expert but that's what Mike Busch says.

Do you have a link that article?  I think Busch knows better, but I'd like to read it.

[PaulB]

1 minute ago, jetdriven said:

Do you have a link that article?  I think Busch knows better, but I'd like to read it.

https://www.cirruspilots.org/cfs-file.ashx/__key/telligent-evolution-components-attachments/13-257-00-00-00-56-36-10/CP-2007_2D00_01.pdf  

Page 2

http://www.eaavideo.org/video.aspx?v=3302992369001

Mentions open oil filler cap around 17:00.  Mentions it around 24:30.  Also responds to a question about it at 43:10

http://www.avweb.com/news/maint/192337-1.html

Not Mike Busch but there's a reference to it in the paragraph under the Ace Pump Sprayer

 

[Bennett]

A few more comments. Before we had the cylinders removed, LASAR did at least two borescopes of each cylinder. Nothing abnormal was observed except that the interior of the cylinders appeared darker (black) than normal. For what it's worth, I have a oil water separator that works just fine, and I use fine wire plugs, and they never oil foul. So, everyone's conclusion is that these chrome cylinders were never properly broken-in. My airplane had one owner prior to me, and he had the engine overhauled. He did spend a great deal of money in well equipping the airplane (before I changed everything in paint, avionics, and the interior), and I am sure that he believed that chrome cylinders were a good idea at that time. Unfortunately, the ring to cylinder wall seals were not good. The cylinders have a choke, and at TDC, the compressions appeared really good. All the cylinders, when pulled, exhibited the same "blackness", so I concur that these chrome cylinders were a mistake.

[jetdriven]

1 hour ago, PaulB said:

https://www.cirruspilots.org/cfs-file.ashx/__key/telligent-evolution-components-attachments/13-257-00-00-00-56-36-10/CP-2007_2D00_01.pdf  

Page 2

http://www.eaavideo.org/video.aspx?v=3302992369001

Mentions open oil filler cap around 17:00.  Mentions it around 24:30.  Also responds to a question about it at 43:10

http://www.avweb.com/news/maint/192337-1.html

Not Mike Busch but there's a reference to it in the paragraph under the Ace Pump Sprayer

 

I still dont get how .2 or .3 PSI (ram air pressure) can force its way into a nose crank seal and overpressure the crankcase to where oil is leaving the breather.  In the case of Mooneys, the flow is forwards, any leaking crank seal oil comes out the front and onto the windshield, because Ive had that happen. I may have to write Mike and ask him, but I cant see it.

[Guest]

8 hours ago, jetdriven said:

I still dont get how .2 or .3 PSI (ram air pressure) can force its way into a nose crank seal and overpressure the crankcase to where oil is leaving the breather.  In the case of Mooneys, the flow is forwards, any leaking crank seal oil comes out the front and onto the windshield, because Ive had that happen. I may have to write Mike and ask him, but I cant see it.

I've heard this one before and find it hard to believe.

Clarence

[Bob - S50]

MB65E:  Compressions are good.  Consumption has stabilized again.  We already use Camguard.

Yetti:  No, we did not switch back.  We are still using the Phillips 20w50 XC.

Jose:  Thanks.  We have the mechanic change the oil (with 4 of us splitting the cost, it isn't worth our time for what we save) but I'll see what he thinks about doing that.  Or maybe my partners and I will change it next time.

RatherBflying:  Already have a JPI EDM 730.

Bennett:  Sounds like you had the top done recently.

All:  Thanks for the input.

Bob

[Piloto]

On ‎4‎/‎25‎/‎2016 at 2:19 PM, teejayevans said:

 

 

1. A week sounds excessive to me, I'd bet 24 hrs would be enough.

5. I'm surprised you don't use 100 here in south Florida?

In the summer 15W50 takes at least a week to drain down completely. When completely drain the oil level raise by about 1/3 of qt. on the dipstick. In winter time 40F it will take at least two weeks to fully drain down.

I use 15W50 because of my flights to KAGC and KRDU during winter.

José

[Raptor05121]

On 4/25/2016 at 9:39 AM, Bob - S50 said:

Here's the question.  Would you do a top overhaul because of excessive blowby?

Not by itself, just my $0.02