Oily Lower Plugs O-360

[Drumstick]

I have had the aircraft for about 4 weeks now with 30 hours since picking her up.  1600 hours on the motor.  Compressions all mid 70s.  Engine is normally flown at altitude with WOT, 2500 RPM and leaned until the engine runs rough and then advanced until it smoothes out.  CHTs sometimes climb up to 460 during climb out but all are stable below 390 in cruise.  Oil consumption is about 1 quart every 5 hours of flight time and seems to "get dirty" after about 10 hours and is dark black by 25. 

Previous owner cautioned about fouling plugs and recommended burning out during a lean run up if the mag drops "passed" but felt rough.  We both lean aggressively on deck.

Flight last week showed a #1 EGT higher than the others and the G2 data showed that during the flight EGT ran about 100 deg higher and CHT was lower than the rest.

During inspection, the lower plugs (REM37BY) were annotated as being oily.  I pulled them today and indeed they are oily.  I'm guessing that burning off this oil is what the lean run up is burning off.  Plugs have been in service for 60 hrs.

So my guess is that the oily plugs is not "normal" but using the lean run-up procedure is an acceptable way of resolving the issue.  What is a more permanent fix to all four lower plugs being covered in oil?  I am considering Tempest fine wires at the moment and cleaning and rotating at every oil change.  I have files uploaded to Savvy but have not purchased the pro package yet .

Thoughts?

Edited February 20, 2017 by Drumstick

[Yetti]

Harbor Freight has a hand held air powered spark plug cleaner that works pretty well.   Are you aggressively leaning on the ground?

[Drumstick]

2 minutes ago, Yetti said:

Harbor Freight has a hand held air powered spark plug cleaner that works pretty well.   Are you aggressively leaning on the ground?

Yes - I think.  If "aggressive" means pulling the mixture back so far that you have to increase the mixture in order to advance the throttle over about 1100 without causing roughness.

And harbor freight is also about a $40 round trip in fuel.  So is there an amazon or spruce equivalent for 20-30 bucks?

Edited February 20, 2017 by Drumstick

[Yetti]

http://www.harborfreight.com/pneumatic-spark-plug-cleaner-32860.html

 

Get the media for it also.

 

HF ships stuff.

 

[Yetti]

Are all cylinders like that?  You might think about buying a cylinder and then rotating it in and doing overhauls on the other ones as they start to need it.

[DonMuncy]

16 minutes ago, Drumstick said:

Yes - I think.  If "aggressive" means pulling the mixture back so far that you have to increase the mixture in order to advance the throttle over about 1100 without causing roughness.

And harbor freight is also about a $40 round trip in fuel.  So is there an amazon or spruce equivalent for 20-30 bucks?

Aircraft Spruce has them, but I don't remember the cost.

[Mooneymite]

If you're going to buy fine wire plugs, don't waste your money on the plug cleaner...

 

[Drumstick]

1 hour ago, Yetti said:

Are all cylinders like that?  You might think about buying a cylinder and then rotating it in and doing overhauls on the other ones as they start to need it.

 

They (lower) are all like that.   Is this from the cylinder wearing out?   How does one known if "they need it"?

Edited February 20, 2017 by Drumstick

[Piloto]

Oil on the bottom plugs is due to worn piston rings or intake valves bushings. There is nothing else you can do.

José

[MBDiagMan]

As Piloto says, oil is making its way into the combustion chamber.  This is the only explanation.  Cylinders/Pistons/rings is the cure.  Leaning on the ground will help some, but not much.  Leaning is the cure for fuel fouling, not oil fouling.

Be advised, that if you choose to use a bead blaster plug cleaner, go to all lengths to see that a glass bead does not remain on a plug.  They are too small for a filter to catch and can continue to circulate, doing damage as they go.

[Marcopolo]

Am I the only one that has a problem with his CHT temp at 460 during climb?  Not sure what model this is but I don't think it matters in this case.  Aluminum and Steel tend to separate at temperatures close to this, and we are assuming his gauge(s) are accurate.

[carusoam]

Drum,

When you get a chance...

update your avatar data to include...  M20C

This will help people understand what your challenges are better.

460°F is not terribly unusual for a C with a dog house.  It isn't magically better for a C than any other plane.

When it comes to oily plugs and what causes them, it starts with the high CHTs and wearing rings and valve guides...

the lower plugs are affected because of gravity.  The engine sits for days.  Anything that drips during this time heads down hill.

PP ideas only, not a mechanic.

Best regards,

-a-

Edited February 21, 2017 by carusoam

[mike20papa]

1 hour ago, Marcopolo said:

Am I the only one that has a problem with his CHT temp at 460 during climb?  Not sure what model this is but I don't think it matters in this case.  Aluminum and Steel tend to separate at temperatures close to this, and we are assuming his gauge(s) are accurate.

I've given up on making this point .. for my flying, CHT's reaching 400 at any time are reason for concern.   No reason a plenum equipped o-360 should "self cook" - unless instructed by owner/operator.  I bet the rings are coked, with no temper left. 

[Drumstick]

9 hours ago, Marcopolo said:

Am I the only one that has a problem with his CHT temp at 460 during climb?  Not sure what model this is but I don't think it matters in this case.  Aluminum and Steel tend to separate at temperatures close to this, and we are assuming his gauge(s) are accurate.

Airplane is new to me (like a month ago) and I was instructed that CHT over 400 during climb is not uncommon and acceptable provided they return to under 400 at cruise.  Previous owner had the airplane for the last 10 years and casually reviewing the G2 data over the last 5 years shows that they flew the airplane exactly the his way.  CHTs in the low to mid 400s at the last part of the climb out and then cruised with temps in the 380-390 range.   

Other than wet plugs, everything else about this engine is fantastic.   Great power, acceptable oil consumption, good compression etc.   

Is it possible to just do rings or is overhauling cylinders the only way to fix this.   I'm not trying to get this engine to last another 15 years but would like to reach TBO at a minimum and hopefully farther.  Currently 1600 SMOH in the year 2000 and 3600 since new.

Edited February 21, 2017 by Drumstick

[Bob_Belville]

IMNSHO, CHTs are too high, even for a C model with dog house. I am still tweaking baffle and baffles seals after 5 years of ownership. (I've been able to reduce climb and cruise temps significantly w/o sacrificing speed. And we're going to make another mod to the cowl today.)

There should be threads here on the subject and maybe a C owner will make you a list of things to check to improve cooling.

• Repair and seal dog house.
• Check cowl flaps, perhaps rig them to be 1/2" open in the closed position.
• Check oil cooler and vernatherm valve. (What is the oil temp at the top of your climb?)
• Increase climb IAS.

[MBDiagMan]

I grew up in my Dad's independent auto repair shop in the fifties and sixties.  That was the day of engine overhauls.  Something that is rarely done on cars today.

In those days, we would take the head(s) off of an engine and measure the bores.  If they were within proper specification, we would replace the rings without boring or replacing Pistons.  If they weren't okay the engine would be torn apart the rest of the way for rebuild or a remanufactured engine installed. From my old world AUTOMOTIVE experience one would think that the same thing would be practical on an aircraft engine, but I have never seen it done.  It might very well be illegal to do so without having the cylinders reconditioned and new Pistons used, providing yellow tagged parts.

From my auto experience and what I have read in this thread, I believe it is very possible that the overheating of the engine being discussed, may have overheated the rings causing them to lose their tension.  That said, one thing I have learned about auto engines is that you never know what it will need until you take it apart.  Then it is peeling the onion.

Hope this is helpful somehow.

[DXB]

20 hours ago, Piloto said:

Oil on the bottom plugs is due to worn piston rings or intake valves bushings. There is nothing else you can do.

José

Yup.  BTW I've heard about the intake valve guide problem causing oil recirculation in the combustion chamber but I'm not sure how common it is.  I asked the shop that just reconditioned two of my jugs, and they seemed to think it is very rare on the O-360s.  

3 hours ago, Drumstick said:

 CHTs in the low to mid 400s at the last part of the climb out and then cruised with temps in the 380-390 range.   

Other than wet plugs, everything else about this engine is fantastic.   Great power, acceptable oil consumption, good compression etc.   

Is it possible to just do rings or is overhauling cylinders the only way to fix this.   I'm not trying to get this engine to last another 15 years but would like to reach TBO at a minimum and hopefully farther.  Currently 1600 SMOH in the year 2000 and 3600 since new.

I just went through something similar.  I would not overhaul cylinders - makes no sense with new cylinders being relatively cheap. If the cylinders are first run, you can IRAN them - will cost $300-500/cylinder, plus a ton of labor. Might end up totaling 6-8amu to do all 4. Keep in mind if a crack is found after they are pulled and cleaned, you will need a new one.  But that's a lot to invest in a 1600 smoh engine. Since you have issues with all 4, in your shoes I might just live with it and monitor closely until the engine gives you another reason to overhaul.  I just did 2 cylinders on mine (burnt exhaust valve on one, oily plug on another), but I have 800 smoh and am hoping the investment will get me a lot more use. So far I'm satisfied with the decision since oil consumption dropped from <3hrs/qt to >10hrs/qt and oil no longer turns black  quickly.  

BTW i think the prior owner's operating experience and yours with the CHTs is pretty typical for Cs, but it's no wonder that we end up needing so much cylinder work with those temps.  I tightened up my doghouse further when the cylinder work was done, but it seems to have made zero difference.  I know other folks have reported better results from baffling work, which I think is worthwhile, but after much effort I've come to the conclusion that it's an intrinsically bad design on these old carb'd planes. 

[Andy95W]

3 hours ago, Drumstick said:

 

Is it possible to just do rings or is overhauling cylinders the only way to fix this.   I'm not trying to get this engine to last another 15 years but would like to reach TBO at a minimum and hopefully farther.  Currently 1600 SMOH in the year 2000 and 3600 since new.

Yes.

You should get the cylinders honed and install all new rings.  To get the cylinders out, your dog house baffling will need to be substantially disassembled.  That would be a very good time to begin addressing holes or ill-fitting pieces of the baffling. When the guy said it was not uncommon for the CHTs to go above 400 in the climb he meant up to 420 or so, not 460.

While the cylinders are out, they will inspect the valves.  I suggest you have them remove the exhaust valve and ream the exhaust valve guides.

This should take you to TBO.  I wouldn't push it too far past TBO, however, but be glad for the 400-500 hour extension.

[Drumstick]

2 minutes ago, DXB said:

I've heard about the intake valve guide problem causing oil recirculation in he combustion chamber but I'm not sure how common it is.  I asked the shop that just reconditioned two of my jugs, and they seemed to think it is very rare on the O-360s.  

I just went through something similar.  I would not overhaul cylinders - makes no sense with new cylinders being relatively cheap. If the cylinders are first run, you can IRAN them - will cost $300-500/cylinder, plus a ton of labor. Might end up totaling 6-8amu to do all 4. Keep in mind if a crack is found after they are pulled and cleaned, you will need a new one.  But that's a lot to invest in a 1600 smoh engine. Since you have issues with all 4, in your shoes I might just live with it and monitor closely until the engine gives you another reason to overhaul.  I just did 2 cylinders on mine (burnt exhaust valve on one, oily plug on another), but I have 800 smoh and am hoping the investment will get me a lot more use. So far I'm satisfied with the decision since oil consumption dropped from <3hrs/qt to >10hrs/qt and oil no longer turns black  quickly.  

BTW i think the prior owner's operating experience and yours with the CHTs is pretty typical for Cs, but it's no wonder that we end up needing so much cylinder work with those temps.  I tightened up my doghouse further when the cylinder work was done, but it seems to have made zero difference.  I know other folks have reported better results from baffling work, which I think is worthwhile, but after much effort I've come to the conclusion that it's an intrinsically bad design on these old carb'd planes. 

 

The engine was factory overhauled and zero timed 17 years ago.  Does this mean they are first run cylinders eligible for IRAN? 

[mike20papa]

Dog house areas to check:

1.  Does your engine have a lightweight starter?  The baffle only fits the original boat anchor starter.  Look to see if this area has been reworked to close excessive original opening when installing a lightweight starter.  

2. Does your engine have a replacement alternator?  The baffle only fits the original generator.  Look to see if this area has been reworked to close excessive opening.  Note: you have to drop the lower cowling to do this with any success.  A can of instant magic spray baffle will not work, but AC Spruce sells wool, .o32 2024T3 and pop rivets.

3.  Examine the area around the alternator/generator bracket and the prop oil line.  Put your newly acquired skills utilizing sheet alumn. wool and cuss words to close off the gaps/hole inherent to this area. 

4.  Check - and more than likely - get ready to replace the silicone baffle material that seals the plenum to the front cowling.  This has to be sealed continuously and carefully checked each time the cowling is removed to be sure the flexible baffle is in the formed U channel retainer - TOP & BOTTOM, SIDES of front cowling.  I lube mine with silicone grease to keep it free moving with engine vibration.

5.  Check the obvious areas around the dog house perimeter and for worn out sht mtl screw tinnermans.

 

 

[Oscar Avalle]

30 minutes ago, DXB said:

Yup.  BTW I've heard about the intake valve guide problem causing oil recirculation in the combustion chamber but I'm not sure how common it is.  I asked the shop that just reconditioned two of my jugs, and they seemed to think it is very rare on the O-360s.  

I just went through something similar.  I would not overhaul cylinders - makes no sense with new cylinders being relatively cheap. If the cylinders are first run, you can IRAN them - will cost $300-500/cylinder, plus a ton of labor. Might end up totaling 6-8amu to do all 4. Keep in mind if a crack is found after they are pulled and cleaned, you will need a new one.  But that's a lot to invest in a 1600 smoh engine. Since you have issues with all 4, in your shoes I might just live with it and monitor closely until the engine gives you another reason to overhaul.  I just did 2 cylinders on mine (burnt exhaust valve on one, oily plug on another), but I have 800 smoh and am hoping the investment will get me a lot more use. So far I'm satisfied with the decision since oil consumption dropped from <3hrs/qt to >10hrs/qt and oil no longer turns black  quickly.  

BTW i think the prior owner's operating experience and yours with the CHTs is pretty typical for Cs, but it's no wonder that we end up needing so much cylinder work with those temps.  I tightened up my doghouse further when the cylinder work was done, but it seems to have made zero difference.  I know other folks have reported better results from baffling work, which I think is worthwhile, but after much effort I've come to the conclusion that it's an intrinsically bad design on these old carb'd planes. 

I agree with you. I did whatever could be done to reduce my CHTs . They got better, but are still in the mid 400 during climb and high 300s in cruise. i just monitor them closely, don't allow the CHTs to get over 465 (my problem cylinder is #3). 

[DXB]

29 minutes ago, Drumstick said:

 

The engine was factory overhauled and zero timed 17 years ago.  Does this mean they are first run cylinders eligible for IRAN? 

I think zero time engines can have overhauled components in them.  The engine log and other paperwork should make it clear whether new or overhauled cylinders were used.

[Andy95W]

46 minutes ago, DXB said:

I think zero time engines can have overhauled components in them.  The engine log and other paperwork should make it clear whether new or overhauled cylinders were used.

I seem to remember hearing that Lycoming factory policy was to only use new cylinder assemblies regardless of new, overhaul, or zero time engines.

[Guitarmaster]

1 Qt every five hours seems on the high side.  I go through 1Qt about every 15 hours.

[neilpilot]

6 minutes ago, Guitarmaster said:

1 Qt every five hours seems on the high side.  I go through 1Qt about every 15 hours.

Our O-360 was using 1 qt every 15+ hours.  Then rebuilt one cylinder (low compression due to a burnt exhaust valve) and oil consumption immediately jumped up to 1 qt every 3-4 hours.  After ~15 hours, replaced that rebuilt cylinder with another cylinder and re-ringed piston, and now oil is back down to 1 qt every 10-15 hours.