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O-235 Oil Leak ID Line-Up!!

That all sounds pretty likely. The engine is 1800 hours SMOH. I THINK the jellified oil is coming from the breather pipe, assuming this is the translucent tube at the back of the lower cowling? I’ll check the compression later in the week.

Assuming it IS all the above, is it overhaul time? or smaller fixes?

Thank you!!


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It's been many years since I have been involved with 0-235s. However back then they just kept running until we got tired of wiping the oil off them. As I recall that was somewhere around 2100 -2200 hours. Official TBO is below those numbers.

This is Lycoming's TBO service instruction. https://flymall.org/aircraft/docs/Lycoming-Recommended-Overhaul Times.pdf It appears that they have increased the recommended times since I was active with the 0-235. These times are not considered regulatory in the States for privately flown airplanes such as your use.

You could remove the rocker covers and check how much wobble the valves have in the guides. This will give you some clues as to how much wear and whether the engine should be torn down or not. Look inside the cylinders with a light for scoring on the cylinder walls. This will address broken rings.
 
It's been many years since I have been involved with 0-235s. However back then they just kept running until we got tired of wiping the oil off them. As I recall that was somewhere around 2100 -2200 hours. Official TBO is below those numbers.

This is Lycoming's TBO service instruction. https://flymall.org/aircraft/docs/Lycoming-Recommended-Overhaul Times.pdf It appears that they have increased the recommended times since I was active with the 0-235. These times are not considered regulatory in the States for privately flown airplanes such as your use.

You could remove the rocker covers and check how much wobble the valves have in the guides. This will give you some clues as to how much wear and whether the engine should be torn down or not. Look inside the cylinders with a light for scoring on the cylinder walls. This will address broken rings.

Given the VERY high cost of O235-C cylinders, is having the cylinders repaired/reworked back to spec with new rings etc an option and have others done this?
 
OK, I'm back on the oil leak hunt after doing a load of work and then, in the 2 hour shake down flight (everything worked!!) the engine lost just under 2 quarts of oil, maybe 1.75 quarts.View attachment 41911View attachment 41912 I looked at the pushrod tubes and the front starboard one is leaking and I've attached a picture. I'm about to order replacements, but could this leak account for such a large oil loss?

My advice would be to lovingly wipe off all the oil after each flight, and enjoy that plane until you are ready for an overhaul. I believe you have to pull the cylinders to change those pushrod gaskets and you don't want to do that unless you are ready for a major overhaul. O235 cylinders often have a benign 1/2" crack at the spark plug which is fine until you pull the cylinder and see it. They are also happy to fret at the case halves which is fine until you re-torque all your cylinders and bind your bearings. It appears to be a high time engine which is burning oil. There is nothing wrong with that, but it is likely unrealistic to pursue "perfect" with it. Actually unrealistic with any airplane but I certainly understand the desire....
The part about wiping the oil off.. (besides keeping the fire hazard low).. is it lets you have an opportunity to see something really wrong.. like broken exhaust, cracked cylinders, loose parts, etc.
 
My advice would be to lovingly wipe off all the oil after each flight, and enjoy that plane until you are ready for an overhaul. I believe you have to pull the cylinders to change those pushrod gaskets and you don't want to do that unless you are ready for a major overhaul. O235 cylinders often have a benign 1/2" crack at the spark plug which is fine until you pull the cylinder and see it. They are also happy to fret at the case halves which is fine until you re-torque all your cylinders and bind your bearings. It appears to be a high time engine which is burning oil. There is nothing wrong with that, but it is likely unrealistic to pursue "perfect" with it. Actually unrealistic with any airplane but I certainly understand the desire....
The part about wiping the oil off.. (besides keeping the fire hazard low).. is it lets you have an opportunity to see something really wrong.. like broken exhaust, cracked cylinders, loose parts, etc.

Thanks for this and very empathetic!! - Yes, I'm chasing perfection and would rather not be pouring oil in, just to wipe it off!! But the cost and hassle of an overhaul, or a new engine is very scary and if indeed the engine will run with black oil and not suffer any major problems with it, I can live with the pouring in and wiping off and in fact I've literally just fitted a longer oil filler so it's MUCH easier to pour oil in!! Just need to work some magic to reduce the wiping off :)xhb0pVtkQoyjkBkMmisSlQ.jpgbHew1iCcSdWMKx0MgrQyvA.jpg
 

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I ran an O-235C1 to 2600 hours. It burned a quart of oil every 3 hours the whole time I had it. Did lots of cross countries 5 plus hours to 10 hours each way and was pretty consistant. Pulled it and tore it down after it started using a quart every 2 hours on a trip back from Sun & Fun oone year. Compressions were always in the 70/80s. When I tore it down the camfer was worn out of the rings allowing the oil into the combustion chamber and burned. I leaned it all the time except the climb so never had oil plugs.
 
I ran an O-235C1 to 2600 hours. It burned a quart of oil every 3 hours the whole time I had it. Did lots of cross countries 5 plus hours to 10 hours each way and was pretty consistant. Pulled it and tore it down after it started using a quart every 2 hours on a trip back from Sun & Fun oone year. Compressions were always in the 70/80s. When I tore it down the camfer was worn out of the rings allowing the oil into the combustion chamber and burned. I leaned it all the time except the climb so never had oil plugs.

Thanks Steve, I lean right after start-up, go full rich for the mag drop checks and then lean until line up. Lean immediately after initial climb (sometimes during the climb if going high) and only go rich on entering the landing pattern :)

My compressions are 70+ on 3 cylinders and late 60s on 1.

The oil is black black black and goes black soon after an oil change, so definitely blow back. I'm now on the hunt for either cylinder refurb or recently overhauled used cylinders. As it's a C it's only 100hp (when new) unlike the heady 108/118 of the C1 and later versions. I'd consider an engine change, but would be a shame to split the engine/airframe partnership that's been together since 1947 :)
 
The killer for for the 0235 is the cost of cylinders. Their is a STC out there to put L cylinders on a C1 case in Grumman airplanes. Cylinder corner studs must be changed to 7/16”. Seems a no brainer to me at overhaul time with a deviation to a Piper airplane.
 
There is nothing that says that the cylinders must be replaced unless they are damaged beyond repair. With normal wear and no cracks, perhaps replace the valve guides, grind the seats and a good hone job will put them back in service.
 
Oil turning black quickly after an oil change can be caused by excessive valve guide wear. Cover up the holes in the top baffling will help keep things cooler.
DENNY
 
Would this excessive wear also lead to high levels of oil loss per hour too?
Excessive wear of the rings and intake valve guides allows oil to be drawn into the combustion chamber where it is mixed with the gasoline and burned. Due to it's chemical properties some of it burns and some is just expelled with the exhaust. Also the worn rings allows excess combustion chamber pressures to pass the rings into the crankcase creating pressures which blows oil vapors out of the crankcase breather.

Oil is normally consumed in the above manner though prior to the wear occurring the consumption will/should be quite low. Somewhere between 9 and 18 hours to the quart is not unusual.

Your reported consumption is indicating worn oil control rings (the bottom rings nearest the crankcase). Also worn intake and likely exhaust valve guides. Since you reported a reasonably high compression reading on all of the cylinder it is indicated that the top compression rings are still performing their job.

I found this on line: The maximum allowable oil consumption limits for all Textron Lycoming aircraftengines can be determined by using the following formula: .006 x BHP x 4 ÷ 7.4 = Qt./Hr. Your engine .006 x 100 x 4 ÷ 7.4 = 0.324 qt/hr or aprox 3 hours per quart. https://www.victor-aviation.com/pdf/tech-docs/SI1427B.pdf
 
Excessive wear of the rings and intake valve guides allows oil to be drawn into the combustion chamber where it is mixed with the gasoline and burned. Due to it's chemical properties some of it burns and some is just expelled with the exhaust. Also the worn rings allows excess combustion chamber pressures to pass the rings into the crankcase creating pressures which blows oil vapors out of the crankcase breather.

Oil is normally consumed in the above manner though prior to the wear occurring the consumption will/should be quite low. Somewhere between 9 and 18 hours to the quart is not unusual.

Your reported consumption is indicating worn oil control rings (the bottom rings nearest the crankcase). Also worn intake and likely exhaust valve guides. Since you reported a reasonably high compression reading on all of the cylinder it is indicated that the top compression rings are still performing their job.

I found this on line: The maximum allowable oil consumption limits for all Textron Lycoming aircraftengines can be determined by using the following formula: .006 x BHP x 4 ÷ 7.4 = Qt./Hr. Your engine .006 x 100 x 4 ÷ 7.4 = 0.324 qt/hr or aprox 3 hours per quart. https://www.victor-aviation.com/pdf/tech-docs/SI1427B.pdf

Thanks for this! So, based on that 2 hour trip we're above the maximum allowable!! I'm going to the airfield later and will check the inside of the exhaust and also take a look for any more jellified oil in the drip pan, having cleaned it on Sunday :)
 
I know that the Pushrod Tube seals are not the main cause of the oil use, but there is oil leaking out there and I've ordered some replacement seals to at least make a start towards less wiping off :) I found this link http://www.n54sg.com/pushrod-seal-replacement/ but not sure if this applies to replacing the O235 seals? Can anyone confirm this, or even better, share the best way to do this? Thanks!!!
 
Phil that description is for an angle valve engine though yours will be very much the same with just one rocker pin instead of two. In addition to the gaskets for the push rod tubes you will need rocker cover gaskets. It may be possible to reuse the push rod tube retainer spring nut safety lock plate.

While you have the rocker arms off check the wobble of the valves in their guides.
https://www.lycoming.com/sites/defa...termine Exhaust Value and Guide Condition.pdf
 
I know that the Pushrod Tube seals are not the main cause of the oil use, but there is oil leaking out there and I've ordered some replacement seals to at least make a start towards less wiping off :) I found this link http://www.n54sg.com/pushrod-seal-replacement/ but not sure if this applies to replacing the O235 seals? Can anyone confirm this, or even better, share the best way to do this? Thanks!!!
Phil,
Your now out on thin ice, from this discribtion.......... Your now in 0290 territory for oil consumption!
I flew a Citabria(0235), yesterday that has just under 2300 hrs SMOH, and is very tired. 40 min flight. It burned exactly 1/2 quart, jet black oil same as yours. Felt about like an 85hp Continental in acceleration. He is looking for 0320! I just had an old friend top his 0235 in his Cub. Purchased it here in Maine last spring, the 0235 engine soposedly had 1200hrs since new????( Engine shop confirmed all 4 cly had atleast double that time on them) The Ferry pilot lost a mag in Watson Lk, but flew it on to Wasilla on ONE mag! The mechanic found ALOT of odditys with the engine;
To include a cracked clyinder, they then found a rusty cam,
Galled lifter bodys and the list went on forever, He convinced my friend to rebuild it........so they found 4 NEW clyinders down in Texas for $8500.A New Camshaft and lifters, the final tab , including Atlees "hotrod" muffler" was time it was all wraped up he was
nearly $21,000..........
The prop was a 74/50, it now turns it 100 rpm LESS than it did with the woreout engine! The prop is at Dominion right now being repitched to 46". Total nightmare.
He could have bought a nice 0320 WD mid time a few weeks after he made the decision to rebuild, for $10k.
The 150 really makes an airplane out of a Cruiser. Huge upgrade. Simple upgrade. May want to think this out very cautiously..........your pumping ALOT of oil. You could easily be pumping ALOT of $$$$ into a "dead horse" into your old engine?????
In todays world of rip off prices for 0235/0290 parts...........its better to walk away from them and upgrade.
Jm2cw

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I'm looking at doing an exchange from the O235-C to a zero timed O235-C2A. Has anyone done this changeover and is it really a plug and play with the same engine mount/baffles and exhaust? and is the power jump from 100hp to 115 REALLY noticeable? :)

And is the C2A the 108hp at 2600 and 115hp at 2800 like the C1 and how achievable is getting 2800 on take off with a fixed pitch prop?!!
 
Phil,
Your now out on thin ice, from this discribtion.......... Your now in 0290 territory for oil consumption!
I flew a Citabria(0235), yesterday that has just under 2300 hrs SMOH, and is very tired. 40 min flight. It burned exactly 1/2 quart, jet black oil same as yours. Felt about like an 85hp Continental in acceleration. He is looking for 0320! I just had an old friend top his 0235 in his Cub. Purchased it here in Maine last spring, the 0235 engine soposedly had 1200hrs since new????( Engine shop confirmed all 4 cly had atleast double that time on them) The Ferry pilot lost a mag in Watson Lk, but flew it on to Wasilla on ONE mag! The mechanic found ALOT of odditys with the engine;
To include a cracked clyinder, they then found a rusty cam,
Galled lifter bodys and the list went on forever, He convinced my friend to rebuild it........so they found 4 NEW clyinders down in Texas for $8500.A New Camshaft and lifters, the final tab , including Atlees "hotrod" muffler" was time it was all wraped up he was
nearly $21,000..........
The prop was a 74/50, it now turns it 100 rpm LESS than it did with the woreout engine! The prop is at Dominion right now being repitched to 46". Total nightmare.
He could have bought a nice 0320 WD mid time a few weeks after he made the decision to rebuild, for $10k.
The 150 really makes an airplane out of a Cruiser. Huge upgrade. Simple upgrade. May want to think this out very cautiously..........your pumping ALOT of oil. You could easily be pumping ALOT of $$$$ into a "dead horse" into your old engine?????
In todays world of rip off prices for 0235/0290 parts...........its better to walk away from them and upgrade.
Jm2cw

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Just seen this post TurboB and after I posted my last one about the C2A. Yes, I like the sound of the O320, but all the hassle of the exhaust, baffles, ancilliaries and propeller puts me off. Is it REALLY such a SImple upgrade? If yes I'll look into it again :)

I loved the effortless power of the O360 in my Pitts and would love something similar in the 12 :)
 
Just seen this post TurboB and after I posted my last one about the C2A. Yes, I like the sound of the O320, but all the hassle of the exhaust, baffles, ancilliaries and propeller puts me off. Is it REALLY such a SImple upgrade? If yes I'll look into it again :)

I loved the effortless power of the O360 in my Pitts and would love something similar in the 12 :)
The Kenmore STC includes simply welding sleaves onto the LOWER engine mount tubes, uses the same stock exhaust, Kenmore calls for PA18 feathers. ( this is a great mod on its own!) Some of the other STC's for an 0320, dont even require the larger tail surfaces...An 0320 is a huge boost in performance. Parts are available all over. No comparison in resale value.
Very simple , easy mod. Baffling can probably be modified from your 0235.
Plus it gives you ALOT of prop options, the 0235 just doesnt have. ( Standard 74" for sale everywhere over here)Best mod you could ever do to your Cruiser Phil! [emoji2]


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The Kenmore STC includes simply welding sleaves onto the LOWER engine mount tubes, uses the same stock exhaust, Kenmore calls for PA18 feathers. ( this is a great mod on its own!) Some of the other STC's for an 0320, dont even require the larger tail surfaces...An 0320 is a huge boost in performance. Parts are available all over. No comparison in resale value.
Very simple , easy mod. Baffling can probably be modified from your 0235.
Plus it gives you ALOT of prop options, the 0235 just doesnt have. ( Standard 74" for sale everywhere over here)Best mod you could ever do to your Cruiser Phil! [emoji2]


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WOW!!! VERY compelling and I’m actually excited at the prospect!! Feels like a proper hop up upgrade too!! THANK YOU!!!


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[emoji6] Your certainly welcome Phil, I have all the drawings for the Kenmore STC if that will help? Just start looking for a good 0320!
Cheers
E

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And I’m guessing you mean the 320 will really INCREASE the resale value?!!

Could you possibly PM me the drawings please? Or I could pm you my email address? Thank you again :)


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And I’m guessing you mean the 320 will really INCREASE the resale value?!!

Could you possibly PM me the drawings please? Or I could pm you my email address? Thank you again :)


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I will get them out to you Phil [emoji6]
Yes I was referencing resale value, however another big plus is the flat fact that your potential pool of buyers will be much larger. A large percentage of guys that simply will walk right past a standard
0235, and NOT consider it because of the lack of performance loaded. The same guys will often take a hard look at a 12 with
the 0320s. So its a win /win more money/ more potential buyers [emoji2]

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I will get them out to you Phil [emoji6]
Yes I was referencing resale value, however another big plus is the flat fact that your potential pool of buyers will be much larger. A large percentage of guys that simply will walk right past a standard
0235, and NOT consider it because of the lack of performance loaded. The same guys will often take a hard look at a 12 with
the 0320s. So its a win /win more money/ more potential buyers [emoji2]

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WOW!! Sounds very compelling!! I'm looking forward to looking at the drawings!! THANK YOU!!
 
Thanks for this! So, based on that 2 hour trip we're above the maximum allowable!! I'm going to the airfield later and will check the inside of the exhaust and also take a look for any more jellified oil in the drip pan, having cleaned it on Sunday :)

I checked the inside of the exhaust this afternoon, using the Mark 1 testing fingers and the inside felt basically sooty and dry and here’s the evidence :) Any more clues in this finding folks?!!

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Just a guess from across the pond. It appears that the oil control rings may be tired allowing oil into the combustion chambers while the engine is running which would produce black wet spark plugs and a oily dirty exhaust pipe. The plugs getting oily and fouled at start up indicates residual oil in the combustion chamber from the oil control rings and/or worn valve guides. Where is the jellified oil coming from? The breather pipe? This would also be an indication of piston ring wear pressurizing the crankcase. What is the total time on the engine since overhaul? This is a symptom of a high time engine. When you pull the prop through by hand does it turn through compression easily or does it have a lot of resistance? Easily = worn rings and/or leaky valves.

Tested the compressions via turning the prop today. Definite compression on all 4 cylinders, less than the O360 felt, but more than the O200 felt. One cylinder felt slightly more compression than the other 3, which is interesting as 3 in the early 70s and one in the late 60s, so I’d have expected 1 to feel weaker than the others.

Also looked at the bottom half of the engine and the starboard rearward side more oily than the port rearward, any clues?


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Your oil control rings are worn out pumping oil into the combustion chamber where it is being mostly burned.
Wash down the engine to remove all of the wet oil from the outside. Then fly it once around the traffic pattern and look for the oil leak. If you fly it too much the oil will spread around making it difficult to find the leak/s.
 
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